Originally posted by ChooseAName This place does Pentax lens rentals. I don't have any personal experience with them.
I've used cameralensrentals several times. They've never disappointed so far.
Renting a lens that you know that you're going to buy eventually (if you have the money) can be counterproductive, effectively making an already expensive purchase more expensive. On the other hand, since Pentax is so hard to find in stores, it can be a good way to try things out before sinking a considerable amount of money into a purchase. This is more of a gut call for you on a case by case basis.
I like to rent lenses for specific events (rented one for a wedding) and for fun when I know I probably won't buy the lens but want to give it a try. In that way its a good preventative measure against LBA-induced impulse buying.