I was 29 when ds was born, and I'll be turning 32 right around the time the new baby is due. I had more fatigue in the beginning with this pg, but otherwise, I've felt great. I have less heartburn... due to a better overall diet, I think. I haven't had the leg cramps or as much hip pain as I did with the last pg either (thanks, bellydancing!). I also weighed 35 lbs. less starting out this pg than I did the last one, so I think that's a factor! I'm nearly 33 weeks, and am not really all that uncomfortable yet. So, I don't think it's just a matter of age.
But, on a side note, I noticed today that I seem to have a plethora of facial hair. Where oh where did these sideburns come from??? With ds, and even after giving birth, I didn't even have to wax at all (compared to pre-pregnancy). Now I don't dare pull my hair back, or I'm afraid I'll look like Wolverine.