Upgrades are clearly more difficult due to a combination of factors. The biggest culprit IMO is cheap UP and UPDI fares. Front cabins on domestic flights are mostly filling on purchased F.

That said, I have one flight in Y this year out of approx. 34K miles, and that's with PQD under 10 cpm. And that one Y flight (EWR-SFO) I could have upgraded at T-60 when it suddenly went R1. Decided row 4 on a 739 wasn't worth the RPU, since I already had 21A with an empty middle (that was a bad call, btw, those slimlines are miserable).

My keys to sitting up front are flight selection, relentless checking for open R, and jumping immediately on the reasonably priced buy-ups.