Rex Ren was intrigued and envisioned a narrative based on the volunteer efforts, co-writing the story with Daniel Chan under the working title We from July to September 2019.

Principal photography began in October but was suspended in November, leading to shifts in funding and significant changes in the cast and crew before production resumed in September 2020.

It had its world premiere at the 2021 Golden Horse Film Festival on 15 November 2021, and was subsequently released in theaters in Taiwan, the United States, and Japan.

Concerned for her safety, Nam, who is heading to the rallies at Chater Garden with his girlfriend Bell, voluntary drivers Fai and Zoe, and fellow protesters Louis and Mr. Burnism, informs the group that YY might be contemplating suicide.

Although Louis initially objects, believing the Chater rallies are more important, Fai suggests they have a quick look at YY's hometown Kwai Fong first.

Bao assesses that YY is likely experiencing suicidal thoughts, noting that individuals in such states often act within eight hours, and urges the group to find her immediately.

Mr. Burnism calls for help in the Telegram groups, leading many protesters to conduct a thorough search in all other areas of Hong Kong outside of Kwai Fong.

The group rushes to YY's apartment and breaks in, only to find a suicide note addressed to her father, expressing her desire to prove the protests' significance through her death.

Mr. Burnism, who initially escapes, returns to ambush the police, allowing Nam, Bell, and Louis to flee, though Fai is brutally beaten, and Zoe and Bao are arrested.

[4] In June 2019, the Hong Kong government introduced a bill to amend the Fugitive Offenders Ordinance concerning extradition without public consent, which sparked a series of protests.

[5][6] Following the police-civilian clashes, Hong Kong experienced a wave of suicides,[a] beginning with Marco Leung Ling-kit, where numerous young people took their lives to make a statement in support for the protests.

[5][6] The directors and screenwriters of May You Stay Forever Young, Rex Ren, Lam Sum, and Daniel Chan, all participated in the 2019–2020 Hong Kong protests and took part in the rescue operations of the volunteer teams.

[2][20] Ren selected a group of potential amateurs for auditions, including Calvin Tong, whom he approached at a mall,[14] as well as Ivy Pang, Sammi Mak, and Suen Ching, with whom he was already acquainted with.

[2] Ray Ho, who was 14 years old during filming, was approached by the production crew on social media after they saw his interview with the political satirical YouTube channel 100Most.

[14] Due to the ongoing social movement, Ren noted that the public was very sensitive about their filming, and numerous venues denied their requests to shoot.

[15] Filming lasted only several days,[c] and was suspended in November, with only seven scenes completed,[23][25] citing reasons related to funding issues and the arrest of a lead actor during the Hong Kong Polytechnic University campus conflict.

[26] Ren also hosted a meal at his home for the original cast, convincing them to join the revival of the project, with Ho and Tong agreeing to return.

[8] However, after receiving feedback from friends of the filmmakers, the direction changed starting with the second cut, as they felt the original version was too context-specific, requiring viewers to be familiar with the protests to relate with the plot, making it less appealing to a larger international audience.

[37][38] Several local distributors attended test screenings after the first cut and provided positive feedback, but refused to distribute due to political considerations.

[17] Lam Sum referenced Ingmar Bergman's Persona (1966) as an inspiration of the film's approach to genre, noting that documentaries often have limitations based on what interviewees disclose, especially under political pressure, whereas drama can transcend these boundaries.

[11] Rather than merely creating a positive reputation or delivering uplifting messages, Ren opted for a more authentic approach that highlights both the humane aspects of protestors and the ugliness of politics.

[29] Writer Liu Wai-tong [zh] and Catherine Weng of The News Lens echoed his view, describing the film as reminiscent of a wuxia narrative.

[60][58] Weng highlighted that the volunteers acted solely out of a common motive without seeking reward,[58] while Liu emphasized that their actions were driven by a sense of righteousness, comparing the plot to Liang Yusheng's Qijian Xia Tianshan, where a diverse cast of characters share a unified commitment to honor.

[35] Ren explained that he sought to emulate Fruit Chan's Made in Hong Kong (1997) and use film as a medium to convey messages,[25] stating that the production team debated whether the outcome of the protestor's survival or death would lead to themes of desperation or hope.

[63] Film scholar Enoch Tam [zh] used May You Stay Forever Young as an example to illustrate how Hong Kong authorities attempt to regulate the dispositif, allowing only a single voice "entrenched in the state apparatus".

[64]: 183–184  This has led to the deterritorialization of these "forbidden films", cultivating alliances outside of the diminishing dispositif and turning to international screenings, ultimately appealing to a much larger audience that embraces creativity.

[29] James Au of The Stand News described the film as "emotionally delicate", acknowledging its limited budget while commending the chroma keying scenes for their cost-effectiveness, aesthetic appeal, and creativity, as well as highlighting the well-developed and realistic character arcs that culminate in a touching ending.

[31] Similarly, Ryan Cheng of PTS News, who named the film "his favorite Sinophone film of 2021", recognized its lack of industry maturity due to budget constraints and "overly functional" dialogues, while also complimenting the production team's dedication and highlighting how its rawness and imperfections reflect the characters' turmoil, ultimately conveying a powerful message about the "spirit of creative freedom and resistance" among youth in the context of social movements.

[70] While in Liu Wai-tong [zh]'s review for Up Media, he compared the film to Ten Years (2015), praising its rich use of metaphors in the story, dialogue, and cinematography, while asserting that despite its "too many coincidences" and "too one-dimensional" ending, its artistic elements and thematic depth overshadow these shortcomings.

[59] Chou Sheng-kai expressed a similar opinion in his piece for The News Lens, noting that while the film effectively portrays the confusion of the young protesters, it fails to explore political ethics and overly glorified characters, presenting a "poorly developed" and excessively emotional narrative that "interprets the protests in a superficial manner", ultimately deeming the film overrated solely because of its subject matter.