?  sounds like you don't bring a spare set of clothes with you ?

I always have one complete change of clothes, head to toe including spare shoes,  so I have dry stuff to change into if its cold and wet and I want to get out of the cold and wet clothes; and in case the #1 set I'm wearing gets torn or something, I've got the spares. That full set of extra clothes is good enough to wear for the entire trip, not just a T-shirt and shorts.  

I'd guess you mostly trip in mid-summer when its warm, and I guess you can get away with not having a spare set of clothes then- if that's the case, T-shirt seems fine, but I'd prefer a long sleeved shirt that offers better bug protection myself.

I don't normally use that spare set of clothes, preferring to just wear the #1 set, which helps dry out anything wet - If its been hot and the shirt is smelly, I'll go swinning and change into the dry spares, but only until the first set is dry enough to wear.  I usually trip the first week of June, starting around Memorial Day - it is more likely to be wet and cold than hot.