What year/make of car? What do you mean 'prime' it? Gas into the intake manifold? I would check to see if you are losing fuel back into the gas tank after sitting. There is a built in check valve in the fuel pumps that goes bad after time...you can buy an inline valve for cheap to correct this problem.
Also, if you have to constantly boost the car, check to see if your alternator is functioning correctly. Start the car, get a multimeter, and take a reading from the battery. You should be getting around 14V, if not alternator is probably in need of a change/rebuild. It wouldn't hurt to check the condition of your battery. Canadian Tire does this for free as long as its out of the car....