I have a 2000 Heil central air, Model CA5530VKD2. All I've done to it in 11 years is keep it free flowing and clean. Would it be advisable to add 1 lb of R22 to it? We have over 1 week of 95-102 degrees starting tomorrow. Right now the duct outlet air temp, mid-cycle, is around 55 degrees on the hottest days. From compressor to evaporator is 10-12 feet.