I recently got my third flat in about a year on my rear wheel. I've patched the other two and decided to get a new tube for the third (left my patch kit at home), but that went flat while I put air in it. I got a replacement and was told it could either be something embedded in the tire or the rim tape.
I've looked at the old tube and none of the punctures are in the rim area. They're all small holes (think pin ******) on the outside so it means something's hitting and getting embedded into the tire. I checked the tire a few times and there appears to be nothing embedded in after checking by hand.
A check of old threads said it could just be a sticker. What puzzles me is the presence of the weird slash marks on the tire. It's like diagonal slashes that appear every so often on the tire itself. I noticed them around the time of the first flat; I thought they were there because I briefly rode the bike with a flat to get home.
Here's the thing though. I ride a 2009 Rockhopper that I bought in 2010, which, if my sources are right, means they're three year old tires (delivered to shops in 2008). I've since put about 1000 miles and God knows how many by prospective owners; should I start to get new tires? I do mostly city riding in a relatively rural town. Either way, I'm going to keep the rim tape on.
TL;DR: I'm getting a lot of fast flats the size of pinholes. Are they related to my rear tire being worn or am I just unlucky/a bad home mechanic? They seem to happen near when I park outside a certain area under a tree.