Different tea bags may vary, but I'd stick with using about 4 tea bags for a full bottle of gin, and letting it steep for about 2 hours before checking in on it to see how it tastes (I've seen elsewhere to not go further than 8 hours of steeping). Using 10 tea bags is quite a lot - you can always add more and adjust as you go, and not so much the other way around (unless you have more bottles of gin around to water it down! Alternatively, you can always cut open the tea bags if you really want to get exacting with it - even then, 4 tablespoons of tea to steep for 2 hours (and up to 8 hours) will do it!