You don't say how many miles are on your current tires, but that may be one place to start. It's pretty common for tires that are near the end of their lifespan to start developing flats, especially the rear because it shoulders the most weight and especially in wet weather when your tires pick up more junk off the roads.

I'm assuming you've changed your tires in those years because while I've seen some tires that are pretty long-lasting, I've never seen/heard of any that will give you 10,000 miles -- half that if you're lucky.