prevent battery from dying when vehicle isn't driven?

I took it to the dealership the next day and a complete diagnostic was done. The battery is in good shape. Was told the electrical system continues to work even with the engine off. Advised to start the vehicle at least every couple of days. Going on vacation tomorrow for 2 weeks. Based on recent experience, I don't expect the suv to start when I return. Will have to call roadside assistance again. Wasn't expecting this issue when I purchased the vehicle. Thanks for your input.

2014 Santa Fe. with 20,000 miles. The battery was just replaced for the 2nd time in less than a year and today the car is dead again. The Dealer had it for four days a month ago, and finally replaced the battery, after going through the entire system. Looks like it will go back to the dealer tomorrow on a tow truck. It will take a trickle charge, but if it sits for 2 days, it is dead.