The power sun is an MVB bulb, so should last longer than a regular UVB bulb, but keep in mind that 18mos. is probably the longest you should keep it before you replace it. It also is more expensive, but it really is one of the best for the price. It also gives off really good heat in addition to the good stuff, so you might or might not need the heating pad with it.
How big is your tank?
1 Doberman Mix: Emmy, 2 DSH Cats: Rowan & Jacob, 1 Bearded Dragon: Rainier (aka Mista Lizad Man), 1 Eastern Box Turtle: Greta, Two 5g tanks: Alchemy (Halfmoon) and Custard (Yellow VT)