My Pug 306 was sat for 3-4 years and the tyres were vibrating like frick for a mile or so. I booked it in for an MOT and by the time I reached the garage, the tyres seemed to have sorted themselves out. It failed on rear brakes and parking brake, and is booked in next week to get this all sorted. I think 6 months will be fine so long as you disconnect the battery.
My biggest concern, if it was just being cold started every week or so and not propery warmed up, would be moisture sitting in the exhaust. The OEM is made of tin foil as it is.