It really depends on your particular car and, perhaps, if you have electrical gremlins. Having read about battery drain, etc, etc, etc, I was expecting the worst in the early days when I left my car for just a few days. Now I confidently leave my 1997 petrol for two weeks at a time, and recently left it parked-up for five weeks. Lovely baby hasn't let me down yet!
Re your specific question about suspension - I'd leave it normal. It will probably be down somewhat by the date of your return, but at least it will have had fun getting there.