My question is: when do the e-upgrade credits actually expire? Do they expire on Feb 28 or do they expire on March 4 for Elite and March 7 for SE?

I am flying on March 1 and have a number of unused credits. Does anyone know if I request an upgrade prior to their expiry (since theoretically I could be given the upgrade as early as Feb 26) but if I am wait listed the credits would not be used until March 1.

Thanks