Yo,
Where I'm from, the squats that would host art events and concerts and stuff would last maximum a couple of months, in general. However, the guys who were running them were well aware of that, so they kept having those shows until they got kicked out. Basically that was when legal action against them as taken....
I probably don't know the squatting scene in your area, but I'd say if you are able to hook up with folks that have already hosted events, there's a good chance they would let you have you show/concert/whatev's