Replacing the battery seems kinda straightforward. Is it fair to assume that upgrades to 530/830/similar mostly concern functionality other than basic route following?
I dont rember what the 520/30 difference was. But I think the 520 was ok in terms of stability. My 530 has been rock solid. Worth checking reviews first.
Etrex are bombproof, so would be annoying to get a dud.
As long as battery not rubbish. I use a 530 for similar.