To maintain the licence you need, at minimum, to pass one one-hour test every two years, no other flying is needed. The twelve hour stuff is just if you don't want to take the test.
Errrrrrrr.....currency....competency....continuity?????
Why would anybody want to spend a small fortune on a PPL to fly a test once every two years????????
Why would a school give you a discount that amounts to a high rate of interest on the money they're borrowing from you? - because they've already tried the bank, and got told "no"
All businesses (not just flight schools) offer discount for money up front bulk orders. It's got nothing to do with the banks refusing loans (with all due respect, what a load of tosh). It's because businesses value confirmed sales and because up front money eases cash flow, thus they offer premium rates for advance sales.
Many (most...all) flying schools offer up to 25 percent discounts for blocks of lessons or complete courses. It's up to the student to do due diligence on the company and its trading history.
That said, in the current climate, pay as you go is a sensible option, but don't beat up on the flying schools for their promotional rates...it is exactly the same concept as the pricing you see everyday in a supermarket.