Seeing that my subscription ran out, I had the chance to test the theory mentioned above and I was right - "Jak & Daxter Trilogy" can indeed be exploited. "Buying" the discounted constituent parts erases the standard PSPlus timer and saves them to your downloads list as normal purchases. The games stay there and remain functional despite the fact that they shouldn't work past the PSPlus subscription expiration date. The game is still on the store, so if you want to have it "for free and for good", try the above.