You shouldn't have to replace those bulbs every six months unless overdriving them. 12-14 months is reasonable.
I personally go a year, try not to exceed. Thinking of a slight bulb combo myself, 2xP+, 2xABS, 2xB+
Haven't purchased yet, but may do KZ 2xC+, 2xSB, 2xFP
I have had tremendous success with that KZ combo, I tried the FP back in 2006, fell in love with results, but they are expensive, I may need to design my bulb swap out around KZ's anual 25% off sales with vendors.
ATI are still amazing in their own right too