Try thinking about the life of the SEAT, not the use with this one bubs.

I have no car but i had a rear-facing capsule that came with the pram (a "travel system" from Graco) and when DD outgrew it i bought a 1+2 stage (9months to 5 years) seat to replace it. Some of the times i used it:

When i was heading for PND and a good friend offered to come and take me and DD out of the city and away from XP (who i was in the middle of splitting from and who was hastening the PND in) for a day.

When my Dad was visiting and he wanted to take me to the beach to walk in the surf like we did when i was a teen - it is one of my most precious memories, BFing her listening to the surf...

When i needed to buy food and the cheapest/best supermarkets charged a lot for delivery and the only other option was to buy small quantities at WAY poorer value because i couldn't carry the larger amounts with DD in the wrap (i buy 36 tins of tomatoes at a time!).

When i needed to get DD to her father's house (after the split) but had a stress fracture in my foot and was NOT able to push or carry her the 2 miles to get there.

When, in the midst of a storm complete with 70mph gales and 90mph gusts (20 tiles came off the roof!) DD had to be gotten BACK from her father, who had to go to work, and the buses had stopped running (high-sided and several had been blown over). DP came and got me and the seat and we went and got DD.

Now my capsule is safely awaiting its next charge, and i use her current seat ALL the time. It's installed in DP (who doesn't live with us yet)'s car and we use it to take her out at the weekends (no, we don't HAVE to, but even DD thinks 3 hours in the science centre is more fun than 90mins in the science centre and 90mins on trains and buses), to get her home from her dad, to got to the shops if need be (i try to use the delivery service if i can get enough bargains to make it "pay" for itself or a free voucher because it's better for the planet that way). Despite this she still uses PT with one or other of her parents about 4x/week and i STILL seem to have to walk about 3 miles a day on average Her current seat will last another 3 years (up to 15kg with the harness and then up to age 5-7 with the car's belt fastened over instead, like a booster but with greater side-protection ) and the old capsule will surely do for our next kids (we only plan one or 2 more). It's likely we'll need to buy a booster for DD when #2 is big enough to need her seat, but hopefully #2 will be fine in said booster by the time #3 needs the seat I'll bet if you look in your kitchen cupboards you have a lot of cookware you barely ever use which doesn't keep you up at night.

Bx