Ok have owned house for 10 years. Cental AC is underpowered at best. Had it checked our first summer and guy said all was well and unit properly sized, but it has alway lost ground on hot days, and if you do lots of in and out its much worse. If you turn on when house is already hot to 80 or so it will take at least two days to pull down to 72 (highs in mid ninties lows in upper 70's humidity high.)
Now the coils have iced up. My suspicion is that the incoming air side of the coils is dirty and restricting air flow across the coils.
My question is does that make sense? that dirt restricted air flow is causing coils to ice? When I first started to investigate this substantially worse performance found ice on suction line at condensor, originally suspected a kink where line comes out of house might have been causing enough restriction to mess things up but have eliminated that (was able to relieve kink significantly and found that the coils themselves have ice on them so the ice at condensor is only after long time running...
Several things can cause a coil to ice up. Unfortunately some people imediately think the unit is undercharged. It could be low on refrigerate. A dirty evaporator coil can cause ice. Open up the plenum if you have too, and clean the coil. See if that, along with a clean air filter solves the problem.