Storm Raven said:
Only if the Efreet agree to cast those wishes, which is up to the DM's discretion.
Well, not actually. You see, if the task you want can be done in 1 round/caster level or less (and using a spell-like ability 3 times would take only 3 rounds), it's an immediate task--you command them, they do it, no negotiations, no payment. If it takes longer, you've got to bargain with them (and pay them).
Naturally, as a DM I'd quash this and the Balor Mining.
To get back on the original topic (sorta): Wish as a Spell-like ability is a broken ability also, since:
1. Wish can be used to generate or improve magic items; this has an XP cost of 5000 + 2 * normal XP cost for the item (or improvement).
2. Using Spell-like abilities doesn't cost the creature XP.
Actually, now that I think about this, this make Efreet-gating even more abusive: Gate 2 Efreets, get 6 wishes, wish for 6 rings of 3 wishes. Net: 18 wishes. Now you get 3 and a half +5 inherent bonuses per 1000xp!
Naturally, any DM that allows a party to get away with that is headed for ruin...