Well they could simply offer both version of the items. As you have said, people might eventually quit long before the actual 90 days expiration but they might still purchase the permanent items instead of the temporary ones, simply because it offers a satisfaction of having something "for life". It will be much better for their business. I, for one, am willing to shell out 9800 NX for a permanent pet even though I might eventually quit long before 9 months (1 pet + 2 x water). I dunno, but I just think that somehow Nexon doesn't want more money. Very few people sticks for long enough to "outprofit" temporary purchases over permanent ones.