I own more than I can regularly rotate, and find myself rotating groups instead of individuals.
I've got several of a type or brand for instance, I'll smoke those for awhile then go to another grouping.
Grabow, LHS, French, Italian, English, 1/4 bends, 1/2 bends, straights, meers, whatever group you decide to make up.
I've acquired most of my collection through estate auction on ebay.
Each pipe affords a different potential. Variety is the spice of life, and, all you really need is a couple of Missouri Prides, and you're good. (or I would be)
One constant is my 'group' of cobs. There's always a cob or three in my daily rotation of approx 8 - 12 bowls.
Easy maintenance, dependable performance, comfortable stems.