Funny you should ask - I wish I had an answer!! But let me start by saying if it's working than no need to rock the boat!! And 2 months is nothing!! My first had reflux & slept in her carseat nearly every night until she was 13 months old. She would sleep, starting at 5 months, 12 hours straight in there! No way was I moving her with sleep like that!! My 2nd never had reflux & it was so strange for me to see her laying in a crib like a "normal" baby. LOL!
Now my 3rd - she's 26 months now & *still* sleeping in her carseat - yes, her infant carseat!! No, I'm not kidding. She doesn't sleep there every night but when she's congested (which happens frequently) she asks for her "seat". :( She had reflux pretty bad & slept there most nights for her first year. We were weaning her off it when she got RSV at 13 months & she had such trouble breathing we had her sleep in the seat to keep her propped up. Blah, blah, blah - sinus, ears, bronchiolitis, breathing treatments for RSV again at 20 months - somehow the seat never got retired. She'll go weeks without using it but then she's back in it for another month.
She's small (about 22.5 lbs & 31 inches) so it's not like she's *way* too big for it but it just doesn't seem comfy to me!! But somehow she still sleeps great in it & goes 12 hours straight through. And like you said - it seems like she feels "secure" in there & seems to want that when she's not feeling good. And if it helps - neither of my 2 seat sleepers have had head shape issues. But I sure wish I could "transition" her to the crib! Eventually she WILL be too big for the seat!!
Hold on, let me see if I can get a link for pics I took last week...She had EI, sinus & was on neb for her cough/breathing.