i'm the same way. Like seriously if i could, i wouldn't stop >.> I love the taste of a clean wet pussy. If i could i would eat one EVERY NIGHT! Not to mention the girls i know can't stop saying their guys never do it XD Judging from that i'm sure many other women would love to take him off your hands. Hell i'd like to be used as a sex slave to relieve a woman's sexual tention by doing that every night. It's not common but it is normal. You better hold onto him. Like angel said, he will go fast if you let him go XD
cos i'm sure some other girl will gladly take him off your hands
unfortunately for many women out there, no, it's not NORMAL. It should be, but your guy is special in a positive way. Not unique, but special.