I use D'Addario, and clean after playing. If I'm playing for hours and hours I clean sometimes when I take a break. If I am at home playing alone usually about 20-25ish hours of playtime. Sometimes that's 3 days, sometimes that's 10 days. If I'm drinking while I play it's less time than that. At a gig (not currently in a band) I use fresh strings for every show, always bringing 2 guitars. By the end of a gig I've had at least 8 beers and the beer sweat has totally destroyed the strings, so they have to go. Gigging is a great way to build up D'Addario points!
Accept the consequence of risk