Im not sure there that anyone has really found an 'end' to the quests. Level 50 is the highest that people have gotten a prize from, but you can keep going after that I think. To get that high, you would either have to get insanely lucky and get cheap items or items that you had already for every quest or have a huge ammount of r99 items. Munsterpoo tried Illusens quests, and he had a tons of r99s, and still he failed a couple of times before making it to the 50th one. Ok...done rambling on about that now, it would take tens of millions of NP or lots of luck.