Between the 3 hour limit and the potential waiting period, and this is a first world problem, I may rethink this whole thing. For example, I just flew IAD-ZRH, with a boarding time of 5 PM for a 5:50 PM flight. (There used to be a time when I didn't mind boarding last (even though I am group 1), but now with all of the carry-ons, I don't want to end up with my bag behind me.)

With the 3 hour rule, if it is based on departure time, I wouldn't be allowed in until 2:50 PM, and maybe as late as 3:20-3:30 PM. Getting to the C/D gates takes 20 minutes from the C1 lounge, so I'd have to leave the lounge at 4:40 PM. This makes the lounge visit less than two hours, or maybe less if there is a line. I am using the lounge to accomplish some last minute work and not to pig out on the free food and gulp down the free drinks.

Not sure it is worth it to get to IAD early just to use the C1 lounge.