The way described by the op doesn't work, but you can get a "free" charge on your last ring charge.
Items using charges have a recast timer (16 hours for exp ring), but when using your last charge, the timer goes straight to 0:00:00 (why would they put a recast on something you can't use anymore? heh).
So when your ring is at 1/7 charges left, uses the last one and trade your ring to gate guard right away!
If you're using empress band, you have 3 hours to get to camp and make 2k (and the 1k bonus) with your party, then can use your ring again.
That's not much, but free exp is always welcome.
