2000 XJ Poor heat/Warm AC

First the details: 2000 Limited, Auto, 4.0 liter, 210k miles.
'98 GC fan clutch. Water pump, t-stat (195 degree) and belt replaced last summer. It usually stays around 195 degrees and never runs over 210 degrees. The electric fan functions.
The AC hasn't stayed cold for more than a few weeks since I've owned it (about 4 years). I've had the evaporator, compressor, clutch, and filter/dryer replaced. No leaks are apparent when checked with dye. The condensor looks good. After each repair I had cold AC for a while.
While the dash was out for the evaporator (last summer) I had the heater core replaced.
The fan blows lots of air, but I've replaced the resistor twice along with a section of the wiring.
Although the blend door seemed to be ok, I put a heater treater door in it anyhow, it does open and close fully.
This winter the heat was warm at best. It wasn't that great in previous years, but this winter I had it on full blast almost all the time.
Research says there is no valve in the heater sysem, so that's not it.

Hopefully that's enough detail for someone to give me some ideas. I've spent nearly as much on the AC as I paid for the whole Jeep!

Have you tried back flushing the heater core? Something might have broken free in the cooling system and plugged it up.

As for the ac I would verify all the blend doors are doing what they should and put the ac on some hi lo gauges and see what the readings are. Low should be ~30 high should be ~260psi Edit: with max settings

Also the blend door for the temperature selector is electronic and sometime the motors in them seize up. I had this happen in my 99 and it was stuck for a while until I went and took the little servo apart and spun the motor free and it has worked fine ever since. If you do this don't mess with the gears inside of it.. I did and it took for ever to get them back to the way they were supposed to be...

Well, The heater core was new last year, though it sould still be plugged. I know the blend door is working as is the stepper motor that moves it.

Not sure about the AC readings. Maybe it's time to invest in a set of guages.

Thanks for the reply.