This item can be recharged by trading it to one of your nation's conquest guards (including outpost guards) for 100 CP per charge.
You cannot purchase it if you already possess a similar item.
You can only purchase or recharge it (or a similar item) one time per conquest results tally.
Tips for getting more than one use per day:
The reuse timer is reset when the last use point is consumed. The ring can then be recharged and is ready to use.
The effect of the ring pauses when you log off (like food) but the reuse timer does not. This is useful if you don't feel like xping one day but plan to the next.
If you do not posess an exp ring duing a conquest tally, you may then buy one (drop your ring before the tally).
Combining the previous tips, it is possible to get 4,000 free exp within one 15 hour interval, albeit at the expense of convenience and CP:
Use ring Fri/Sat when at 2/7, log off. Log on before the tally. Gain 3k exp. Use ring. Gain 3k exp. Recharge and use ring. Gain 3k exp. Drop ring and wait for tally. Buy and use ring. Gain 3k exp for a total of 4k free exp.