They can buy themselves about 4 years if they make 7.0 have a level cap of 95 and then 8.0 with a cap of 100. All they would do is figure out how much exp/level for what 90-92, and make that the tnl for 90-91. Rinse and repeat for all other levels.

Personally, level is just a number. iLvl is increasing about 130 per expansion. While that is just a number was well, eventually we'll be creeping into iLvl of 1000+. I don't know if that will be seen as a problem or not.