The tire probably has a slow leak - front tires do not go down faster than rear.

I usually pump up my tires at least every 2-3 rides on my commuter and every time on my road bike/mountain bike before going out for a ride. Tires can lose air pretty quickly. I would fill the tire up and check them every day for a while to see how the tire holds air. If it holds air for 2-3 days, it is a very slow leak and you shouldn't worry about it too much. If it goes down in 2 days, maybe change your inner tube.

spoke