Status lasts a year from the date earned. To get the Identity tier credit (which is what OP is assigning the bulk of the value to here) you can't credit the spend to Marriott.*

End of the day, my comp offers from Cosmo have been very generous based on play anyhow, 4 nights in a Terrace 1BR with F&B credit, waived resort fees, and free valet... again a YMMV situation, but strictly comparing points to points without considering the status perks, it's a better deal for most Bonvoy elite members to choose Bonvoy points over Identity points for Bonvoy-eligible spend.

*of course, you could put *just* the room on your folio and credit that to Marriott for the EQN, and then pay for everything else off-folio and give your Identity card each time to get Identity credit for those transactions one at a time, but (1) you'd likely lose out on some of the 6x/$ credit card points that way, and (2) that sounds like a pain.