Schrader valves had some corrosion and leaked. New valves (cheap) and a recharge a few years ago, and it blows ice cold.
I'm not aware that GTs are more problematic than any other car. One recharge in 12 years seems pretty good to me.
Uhhh, what is "AC fluid"? Does it need to be changed regularly too? :lol
Why did you need new rear shocks and a new rear axle after only 11K miles?