Charges for Miscellaneous Magic Items

Do MMIs have charges or are they essentially permanently powered up?

I'm asking because I have a party with Drums of Panic and I'm trying to figure out how overpowered they're going to be.

Not an autarch, but i think that they are permanently power up.

Any item that doesn't explicitly have a finite number of charges does not have a limited number of charges. Here's my reasoning.

From page 210 of the ACKS core rules:

 Some magic items have limited uses, called “charges.” When items have charges, each charge can be spent for one instance of magical effect. A character will not know how many charges an item has unless he identified the item with Magic Research. When the charges are all spent the item becomes useless and non-magical.

So, "some" magic items have charges - which is to say,. not all of them. There's a whole bunch of magic items that specify that they have charges - for example, the Chime of Opening. Since the rules go out of their way to point out when an item does have charges, presumably the usual state of affairs is that they don't. It therefore seems safe to assume that you only have to worry about limited charges if there's something that says you should.

FWIW, those drums are going to be a pain in the ass for us to use, because the safe zone around them is only a 10' radius, and we're bringing a small army of mercs with us.

They'll be useful in dungeons, and if I ever get the Protection from Normal Weapons spell, someone can just sprint directly through the enemy to do a drum solo once they're far enough away from us

regardless, I think the key is that if you strictly enforce the way the magic item works, the fact that it's constantly re-usable isn't as bad as it seems.