I have a 2014 (so, very old) tesla and the lanekeeping continues to work extremely well. I have literally never had this issue and I live in a rainy area.
So sad that we live in an era of tech where basically everything is expected to severely degrade after 2 years and be essentially unusable after 5.
But the updates do other things too, like help it understand new kinds of signs or to improve handling of weird situations.
I'd be much more likely to buy a car that has pretty good driver assist tech if it were regularly updated. I don't want to have a car for 10 years if half the driver assist tech is useless when the car is brand new, and it will never be updated.