Hi,
I have a 99' montana which had the same problem:
Rear light bulbs not burning because the contacts loose their tension over time. I removed the bulb and used a small screwdriver to bend the contacts closer together. Then I used my wifes electric, hot glue gun and applied a small dab of glue to the outside of the contact; (the space where the contact would bend over to).This glue cools and hardens quickly and I replaced the bulb into the now "tightened" socket. This was nearly two years ago and that quick fix is still holding.
Regards, HC2000