Ah, I didn't see the 85% comment. Yeah 3' intervals at 85% are fine if you are in base and riding for several hours. Generally intervals are interpreted to be above FTP though.

I just calculated and I do think 85% is hard. But just because it is kinda hard doesn't mean much. 85% for me is 276 watts. My last race I averaged 278 for an hour, with NP almost = FTP. And I planned on doing 2 races that day. 8x3' at 85% kinda adds up to junk miles for training.