Don't really know if they are more prone. I have had more flats on MTB tires than 25-28C tires but it may all come down to chance. Riding on patched tubes is not a problem. If patched properly the patched section is actually stronger than the rest of the tube, or so I have been told. At any rate I have never had a patch fail. That being said I would probably limit patches to a total of two on any one tube. No particualr reason other than it fits within my own "comfort zone" vis a vis riding jury rigged equipment of sorts.