I'll need to move my Trend to the end of the driveway and keep it there for a month -- new concrete. I already use a 25 - 30 foot 30 amp extension cord plugged into the power cord (probably another 25 feet long) to keep it plugged into the outlet in my garage. Is it safe to add another cord? Is there a maximum length of cords? All I need is just to get the fridge ready and run the ac before a trip.