Auto Air Conditioning & Heater Repair: 1994 buick century air conditioning, buick century, intricate pieces

Question
My 94 buick century won't hold a recharge.  It has only 68000 miles on it although some rust.  I was wondering if it would be worth it to have the air conditioning fixed even I realize it would be costly. What do you think I should do? And how much do you think this would cost and would it last. I really need air and I really don't want to get a new or newer car.  Please advise on this.  My mechanic thinks it's cheaper to keep doing the recharge but I just had that done and it worked for a week. Thank you.

Answer
 It is most likely the Evaporator core or compressor seals that are leaking.  I do not advise repairs on systems that are more than 10-15 years old depending on the value of the vehicle.  Vehicle AC is not like a window shaker in your home.  The system is strewn over almost the entire car and has many intricate pieces that work together to remove the heat from the air.  Its important to understand that even if you do a 600-800.00 repair you are probably only replacing one or two components in a multi component system.  
 If you were to replace an evaporator, compressor and condenser in a 1994 buick you would easily exceed the value of your car.
 I woudl advise against topping up a system that is leaking that bad.  Its not good for the environment.  R134A is a hydroflorocarbon and promotes global warming.