[fluffything]

I've replaced the battery twice, last time in september 2019, and this last time it costed me 60 EUR, and the battery life is much better than the original one.

I might want to replace the battery again in the next 3-4 years if I still have this laptop, and you might be right in that this might not be possible, but at least today it is.

[Fnoord]

Oh it is likely possible via iFixit or other aftermarket. Just not officially via Apple.

[fluffything]

Yep, I just googled my model + battery, and ordered a new battery from iFixit. Took like 15 min to swap the battery myself.