Ten or fifteen minutes? Are you kidding me? When? I went in may, well I was in france for may and june of 2004. It must of been like our third or 4th day in Paris, so like June 3rd or something.
I don't know I go there a lot
I honnestly can't remember the last time I really had to wait. Given the fact that over 80 million tourists come to France every year I'm guessing the Louvres gets really crowded in august (I wouldn't know since I'm in vacation at that time
Getting into vatican and sistine was also quite long like 50 minutes, but we got tickets before the day we went in and we had our own guide, so that helped us to cut the line wait a bit.
I had to wait over 2 hours but I was there in the middle of july (once again probably not the least crowded month) and it was well worth it