Don't know how much longer I can do this

It takes away the sense of accomplishment.
If someone grinded so hard to level 70, they'll be as proud as hell.
If someone leeches to 70, they'll be like "oh yay finally 4 hours passed an im 70!!!!... wait wasn't I supposed to fee super good good about this... this sucks omg im gonna tell all my friends how greaet this is.... "

It's like, bleh. I'm 70. It's kinda boring since I didn't even try to achieve it, I leeched.

I still felt accomplished when I hit 70 even though I leeched 4 Bigfoots for a few levels in mid-6x, because I was still in charge of training my character, and I never lost the "work ethic" to stop training. Even if the Bigfoots never existed, I would have reached the same point I am at now. It may be significantly easier, but then you'd have to compare training with and without 2x. A lot of the people who are higher levelled than me and have not leeched probably grinded their ass off over Thanksgiving break on 4x. I enjoyed about 12 hours of that exp, and only 4 hours of 4x.

What I'm trying to say is, as long as you're the one training your character, it doesn't matter how you get there.