Yeah what he said. Your bike tires should hold pressure over a season. I have to add air to my motorcycle tires maybe twice a year.
That being said, I wouldn't count on the gauge on a shitty compressor to be accurate. Get yourself an accurate tire pressure gauge and check it over a couple days without riding it in between to make sure it's really losing pressure sitting still. If it is, fill it up and take it back to the dealership and tell them to fuckin' fix it! And don't let them 'fix' it by putting slimy sealant in your tires. That shit is a mess to clean up when you do a tire change, and it's just a band aid. You want to know if they sold you a bike with defective rims or tires, basically.