Veronica runs slime on her road bike. I run Specialized Armadillo (Heavy tires) on my bike because I am slow, who cares about a little extra weight? I am even slower at changing a flat. 
Make sure you are putting proper air in the tire. When my tires were worn (and there is no magical distance/time for a tire) I started flatting like crazy. Check your rims as everyone has said too. Good luck, flats are no fun!
Amanda
2011 Specialized Epic Comp 29er | Specialized Phenom | "Marie Laveau"
2007 Cannondale Synapse Carbon Road | Selle Italia Lady Gel Flow | "Miranda"
You don't have to be great to get started, but you do have to get started to be great. -Lee J. Colan