96 Sportster XL1200 tail light problem?

After start upp, if I squeeze the front/rear brake the tail lights remain on. I have found out that once they become stuck on, if I just barely squeeze the front brake they shut off, and once released come back on. However, when I get on it and ride it, they shut off after about 10 or so minutes and function fine. Any ideas? Could it be the rectifier? Battery? Stator?