How much sleep are 4mth bubbas meant to have?

My CMHN said that 30-45min naps are not long enough.
MJ will have about 3 of these aday, but will not resettle after waking.
The only time she will have a long sleep is when she is in the pram, i do walk most days and leave her in it after we reture (bring the pram in the house) but if she is in her cot or on her bouncer (she likes to rock herself to sleep sometimes) she wonts sleep for long.

Is this OK?