Old guys can be tough... remember you won't be able to sell him as easily as your 24yo, and likely if you keep him a season or two then you will have to sack him. So, they can be good for short term success but long term can be expensive.

Does your current GK get bad ratings? Lost matches for you? Then yeah maybe replace him.

Do you only keep one GK? You could buy your elderly fellow and keep your current on the bench (at least until you know the replacement isn't rotten)