Honestly, with the rate we get EXP these days, there should be very little worries about such things. However where as the climb from 75 to 90 can be done in a matter of days, the old experience point area's despite their massive update are still a bit lacking in such speed.
Lacking as in, i find myself slightly troubled whenever my EXP ring isnt charged and being stuck waiting an entire week to recharge it for a minor boost in experience point gain.
Considering the alternatives, what would be the harm in making us able to recharge exp rings daily? At this point it's not going to break anything. The maximum bonus of 2000 exp per use isnt going to make things extremely unbalanced, it will just be more pleasant to have charges on the ring whenever you need it. There's a 16 hour cooldown to prevent abuse anyhow, and a daily restriction on new purchases/recharges is going to keep people from finding other means to exploit it.
Make EXP rings rechargable daily instead of weekly.
(Or you could also always find a way to make EXP rings more efficient cooldown wise if you find yourself in a very generous mood today.)