I’d say not worth it for upgrades alone. As a TPA based Platinum, I’m running about 35% on upgrades to first but 100% on C+. As a Silver, you wouldn’t be eligible for C+ until 24 hours out, so they would be unlikely, especially if you don’t want a middle seat. First would be even harder, I frequently see Diamonds in the back. Again, times, days of the week and routes flown matter greatly. Perhaps more than status? My silver co-worker has about a 50% F upgrade percentage, but flies off peak times and days. I don’t know what his C+ UG rate is.