Originally Posted by Socratov
If they are gone long enough the bar for great power may have been lowered.
Cutting short most of the long post... No. It's been made quite a point out of the fact that the power levels have risen. Natsu pre-upgrade has problems fighting Max. Sting and Rouge are considered to be levels above that.
I'm rather not trying to come up with explanations for... mostly anything in FT... at least regarding power levels, especially Natsu's... But that's just my take.