Last year I was doing almost 320w for a 20 minute TT. For an hour, more like 275w. I simply wasn’t training enough to maintain that power for an hour and would die a death after 35 minutes if I did. The best home comparison rather than doing an FTP is riding the Alpe du Zwift, you can feel pretty peppy at the bottom, but that last 10-15 minutes is always tough. I did Tour De Zwift race stage 1 tonight in B. Made the front in every split aside from the rollers right at the finish (wattopia flat course). Came in 12th, 6 in front of me rode 4.1w kg or higher... not sure on the rules there, normally that’s an upgrade or DQ!