My DD catnapped most of the time too. We rarely had more than 45mins at a time, though she was like clockwork going to sleep every 2 1/2- 3hrs. Only at night did we get more than an hour at a time. Even right up until she dropped some day sleeps, so until about 11mths, she would only have 3 45min sleeps a day. Now we usually have 30-40mins in the morning and 1-1 1/2hrs in the arvo. Occaisionally she only has one 2hr sleep, but that's not often.
If your DD is alert happy and energetic, I say don't worry!!