By lifespan, do you mean how many times can you recharge it? I don't know yet...
If you want to ask how long it lasts on a charge, I haven't yet managed to drain it completely when I'm shooting two-hour sequences non-stop. I'd estimate that after two hours non-stop, there should still be a quarter of a charge left.
I bought a spare battery too.
It's a FullHD camera, so it's not 4K.

4K is definitely not it. You can recharge the battery. I have had no problems with the battery. Good camera but not professional.

Hello, this is a FullHD cam. Not 4K.
My battery still lasts well. Even after about 5 years.
No idea if there are replacement batteries, never needed any.
Mfg A buyer