I left mine for 4 months in the garage whilst I worked abroad a few years ago, nobody checked on it and it wasn't even unlocked let alone run up.
Needless to say it fired up first time and drove perfectly! Just needed a wash lol.
Having said that I once left my 1.4 Clio for 8 months outside and even that fired up first time, never had trouble with Renault batteries ( touch wood ).
All depends on the battery condition.. if it's fully charged and in good/newsish cond then you can get away with 'XX' amount of weeks/months.. but I wouldn't risk leaving a car 6+ weeks with a battery that may or may not be in good cond.. unless of course your not bothered charging it if it does run flat.
I always used to disconnect the battery on my previous track cars between use as it keeps the battery in better cond (eg less drain + saves battery becoming discharged) and saved me the ball ache of having to charge (+ it's not good to keep recharging and you run the risk of ruining the battery unless using a trickle charger)
Personally I would leave the handbrake off too (put a brick under a wheel or leave it in gear).