I haven't looked the Mirage setup over closely, however cars have rubber hoses and seals in the AC system must have the AC run every so often as the oil in the system is what keeps the hoses from leaking. So if you drive around with the AC off for longer periods in cool weather to save gas it should be cycled periodically to circulate the oil. This won't be a huge leak but slowly occur over time, usually over a couple of years. You notice it a lot up here in northern climates for cars not driven in winter where they sit for several months.