Hoping some TPAC folks can help me here, understanding that this entire thread is as much art as science...

Looking to fly SFO-TPE-SFO on a W fare and hoping to u/g to J with PP (I'm 1K.).

Option one is to go in March, departing on the later flight on a Wednesday, returning on the later flight the following Tuesday. Option two is to do the same but in May.

My slight preference is to go in March, but not if my u/g odds are better in May. Am flexible on days to travel as well. Could do the earlier flights as well if need be.

No idea at all how tough this upgrade is or whether it varies significantly by day/month/time, but I'd like to maximize my odds.

Any ideas? Thanks!