I'm in the process of it right now. FIsh have been in the QT for about 6 days now and todays measurement should have me at 2.5ppm I was planning on the full 76 days. I dont know if 'giving up' after 45 days is worth the risk of having to start over.It's possible they'd be fine as long as they're in good enough health regardless (Paul B and a number of others run their tanks on the philosophy that at as long as the fish are kept in proper conditions with proper feed, they won't die from illness), but it's also possible that it's not velvet.
Yeah, this is why Jay and others recommend doing a full fallow (45-76 days at 81F) period for the tank and a properly conducted, 30 day therapeutic copper treatment and two week observational quarantine afterwards for the fish. It's possible that the velvet could still linger after that, but the odds are extremely low.