Two comments.In general, worry more about the 12V than the 400V battery: if the little one goes flat, it can be tricky to revive the car. If the garage is exposed (i.e. it gets hot in that desert) definitely plug the car in so the airconditioner can keep the battery cool.
Probably not over just two months. I've left cars sit for 3-4 months and they started just fine. Maybe the Smart has a higher quiescent current draw from the battery but then it also does not have to turn a starter motor.Hence my initial response to the OP.