As pop music of the 1960s was re-evaluated by newer generation of critics, Begin continued to receive positive reviews after the album was re-issued in the 1990s, with AllMusic finding it to be a "bona fide lost classic" and that it was on the same level as "more widely popular albums from the era", and Pitchfork declaring it "probably the single greatest 60s pop record produced in L.A. outside of The Beach Boys."

Following the release of Eternity's Children's debut album, Curt Boettcher and Keith Olsen began a new project that included members of The Ballroom and Sagittarius called The Millennium.

[5] Mike Fennelly of the group stated that a "We were very enthusiastic about the creativity that was indeed at a high level for the initial writing, demo and master recording.

[7][8] AllMusic described the genre as a form mid-1960s mainstream pop music that was mildly influenced by psychedelia and combined "rich harmony vocals, lush orchestrations, and relentless good cheer.

"[9] Some of the lyrics and themes on Begin reflect the current world events and personal experiences happening to the members of the group.

[11] Sandy Salisbury described the song "Karmic Dream Sequence #1" as "perhaps the essence of the Millennium experience", by developing music that evokes "feelings from the deepest parts of what we were doing at that time in our lives.

[10][11] Mallory spoke on "Karmic Dream Sequence #1", explaining that it came from a return trip visiting his grandmother for the last time before she had died.

The re-issues of Begin on labels such as Rev-Ola encouraged former Millennium members to contact Joe Foster of Sonic Past Music allowing them access to original demos of the group to be re-released on the compilation album Pieces.

[17] The review praised the production and described the songwriting as "sterling and innovative, never straying into the type of psychedelic overindulgence which marred so many records from this era," specifically noting the song "It's You" to be "as powerful and fully realized as the era ever produced, easily on par with songs by the Beach Boys and the Byrds -- and, yes, even the Beatles.

[15] Reviewing the compilation album Pieces, Dominique Leone described Begin as "probably the single greatest 60s pop record produced in L.A. outside of The Beach Boys.

"[19] Uncut noted that "Boettcher's ability to dismantle and reassemble structures gives the listener infinite possibilities for aural delight," and that "You could write a manual about 'To Claudia On A Thursday' alone, or you could simply lie back and let the cut-up sounds wash over your brain.

[13] "There is Nothing More to Say" has been covered by Chris Knight and Maureen McCormick of The Brady Bunch fame with slightly re-written lyrics.

[21] Former Millennium members Stec and Mallory were still performing songs from Begin in their live shows decades after the album's release.