Depends on (don't you hate it when you wanted a simple answer, but it is not simple) a lot of things:

- rim brakes or disc? (Rim brakes needs a rim to be trued better.)
- how much weight on the wheel? (That is obvious)
- drive side or other side? (Drive side is under more tension on almost all bikes, harder on a rim if you ride without it.)
- surface that you are riding on? (Smooth pavement easier on a rim.)
- how good the quality of your rim is? (Obvious.)
- rime diameter? (I think a 26 inch vs 700c is not much different, but some would say the 26 inch is a stronger rim.)
- how much you value keeping that rim compared to replacing it later? (If you don't care about trashing it, go for it.)
- how far are you going to go? (Shorter distance is better.)

I was in a campground this past August, someone was mountain biking (not touring) on a pretty tough trail. He broke a spoke, was worried about riding teh bike. I asked and he did not care if he had to buy a new rim when he got home (he was car camping). So, we loosened a couple adjacent spokes to make it a bit truer, but he had disc brakes so it did not have to be really true. He then went back out on the trail and started hammering on it again. It was a good rim, I don't think he trashed it, but he drove hundreds of miles to get to that trai for the weekendl, he would have gladly paid for a new rim and the cost to have it put on.