This would loop like a normal [until] that has received a bang to its left inlet, but at the nth iteration (defined by the user) it stops and outputs a message to the console that says it's reached the nth iteration and might be an infinite loop. As far as I can tell you can't implement a similar safety patch around [until] without interrupting the main object chain. This would be better than inserting a [1000( above the [until] object because:
a) you get feedback to the console when it reaches the last iteration
b) when you're done debugging, you don't have to mess with the wires in the main object chain-- you can just remove the "-debug n" part of [until].
It's also better than making a counter because again, you're not fooling with wires in the main object chain.