Toyota Repair: 1995 Corolla a/c not working, toyota corolla, older cars

Question
Hello Ted,

1995 Toyota Corolla DX, 1.8L
Automatic with 220,000 miles

A couple of summers ago the air conditioning cooling began to slowly decline. It stopped cooling completely by the following spring and I recharged the system with 1 can of 134a refrigerant (DIY, I think 15 or 18oz.?? bought at AutoZone) and did nothing else. It worked thru the summer (3 months) then stopped pumping cold air again.

I’m reluctant to have a mechanic fix it due to the cost (the car is almost 18 years old, but in great shape, so I’ll probably keep it however long it runs). Friends have told me they still had a/c problems with their older cars even after spending big bucks to have it professionally fixed.

Questions:
Is it okay to recharge the system again the same way I did it last time to get me thru the summer seasons?

What is the proper amount of refrigerant to put in? Are there any other things I can do to improve performance?

How, if at all, will repeated DIY recharging affect the system? Could it complicate a mechanic’s ability to fully repair the system in the future if I want to pursue that course?

Thank you in advance Ted for your time and advice,
Nick

Answer
The amount in the system is about 1.3 pounds, most likely there is a leak, there is nothing to be concerned about if just recharging it as needed instead of possibly spending  a lot of money to fix it. sometimes a leak can be obvious so visually inspect all the Freon lines and hoses as well as the condenser in front of the radiator, a leak will usually look oily, especially at the fittings where the lines connect to the condenser or the evaporator near the firewall, sometimes a leak is just a sealing O-ring which is easily replaced.