Same here! My DS started taking 2 hour naps when we returned from a trip to the west coast, and I hadn't done anything (except that our air conditioning had broken for 2 days and it was
hot in here). That was around the time he turned 5 mo. Now, he still takes a 2 hour nap in the morning, which is heavenly because I can sleep in if I haven't gotten a good night's sleep. The afternoons, however, are a different story! 30-45 min naps, even if I try to extend them. I just end up getting screamed at in my ear (can anyone suggest any ear plugs?).
I do think that temperament has something to do with it, though. Since he's an angel/textbook baby, it should be easier to try to extend the naps than with other babies.
Start by taking him away from his activity 5 min sooner than normal and starting the wind down then. Also, try pat/shhh just as he's waking up from a short nap and, if he doesn't go back to sleep with that, I'd suggest trying PU/PD for a couple of days. If it doesn't help, let him do what he's doing and try again in a couple of weeks.
Otherwise, just keep his activities a little shorter in the afternoon since his naps are so short. When my DS takes his short naps I just make sure I watch his cues like a hawk and I get him down for a nap even if it's 45 min later.
Sounds like your little guy is doing great otherwise!
HTH :?