If I understand this correctly, the bad battery gave you 700 shots?

I used to shoot indiscriminately when I went digital. Memory is cheap after all compared to the cost of developing film.
Now I seldom have a day over 700 shots. To much sorting, and I try to be selective. A battery that can do 700 shots is good for a day. I might be inclined to keep using it, even if I bought another as a spare for my own piece of mind.

I have batteries six years old now, I haven't paid attention to their strength but they seem softer than they used to be. It doesn't bother me because I have four and always a backup. That's enough to shoot heavy for three days without charging.

I would judge the need by how many days you have to go without charging.