How many times is it safe to use a condom?

Me and my girlfriend have been using our condom now for about a year (around 4 shags). It's starting to look a little threadbare, and I was wondering how many suggested uses a condom has, and when would it be worth us replacing it with a new one? Our next planned session of ual will be on the 24th april, so there's plenty of time to go to the shop for another one, but if somebody could let me know that would be great :)