Submitted an upgrade request using miles for a flight sunday on a 757-200. doesnt look like I will get it as F is full.

Contemplating leaving on a later flight now that day on a 737-800. If I do the same day change tomorrow when I am within 24 hours of the flight, does my upgrade request carry over to the new flight? F is not full but I dont really want to move up front on a 737 using my miles.

If it does transfer, would it matter if I waited to after midnight to do the change request as I think someone told me once that upgrades with miles are only possible up until midnight the day of the flight.

Thanks!