Firs time mom here ... car seat/stroller question

Hi ladies

I have a question. I was wondering when do you stop transferring baby from car seat to stroller? I keep reading that it is not a good idea to let your baby sleep in their car seat for long periods of times. We are looking at travel systems but the stroller that I want can only be used with their car seats (nuna) and I like the maxi cosi

Idk if it would be a good idea to buy a different stroller/car seat and just transfer baby from car seat to stroller.

Keep in mind, we are not buying a stroller until he’s 3 months old because I’m going to baby wear as much as I can and I’ll be giving birth in feb (cold weather) so we won’t be leaving the house to hang out outside.

Any guidance would be greatly appreciated!