Ken, in 5/3/1, the third week can be a time to go for a max without losing a training day. Once you have been doing it for a while, the last set will always be a new max, for practical purposes. If you are worried about getting it, just go up with singles, then do your 85% and 75% sets on the "way down". I think I got that from Wendler somewhere. If you think your true 1RM is higher than the 95% rep on that day, do singles at 80, 90, 100% (or more), then go back down to 3x85 and 5x75.
Ever since I typed that in last night about missing a training day I've been thinking, "Well, hmmm, you could just do the regular workout on the way down...."
I'm not sure Wendler ever said to do that, but once you've been using 5/3/1 awhile, you tend toward certain lines of thinking. It's possible you worked that one out yourself.
Well anyway, wandering around a bit and heading back to the OP, my attitude towards 1RM's has been:
1) Beginning: what else is there, isn't that why we lift?
2) Later: Oh, right, do the sets, test it once in awhile
3) Now: Maybe try a 1RM every 2nd cycle for the fun of it, do the regular sets on the way down.
Which all just goes to show Wendler seems to have gotten through to me and I don't worry about it anymore -- if I'm making the progression during the cycle I know I'm gaining. To be sure, if I'm going to do one I want it to be the highest number I could possibly reach, but when/how often, doesn't seem to bother me much anymore.