I tell the players how many charges an item has when they identify it, including how many recharge when/if they recharge, and I leave it up to the players to keep track.
Sure, they basically never spend the last charge (since situations dire enough to be worth the risk of losing the item are pretty rare) - but in my experience the alternative that happens when the players don't know how many charges something has is the players rarely, if ever, using the item at all, which leaves me wondering "Why did I even give them this item?"