Brakes were replaced 20,000 miles ago, two years ago, and when they get hot the front brakes start to drag. Calper slide bolts were lubricated twice no help in solving problems. After car sets for a couple hours brakes are free again.

 

The caliper bores have probably started to get corrosion and dirt from not changing the fluid.This is causing the pistons to stay pressed against the pads and dragging the pads against the rotors.
I had the same thing happen last year for that same reason.The remedy? I pulled the calipers and cleaned the bores using 400 grit sandpaper then put everything back together.You can buy rebuilt calipers if you don't want to DIY.Calipers can be expensive though,I only had the cost of new fluid as far as money spent.About three hours of time were spent also.

 

What grease did you use to lubricate the caliper pins? It must by high temp synthetic grease. Conventional chassis grease will deteriorate at high temps and cause the pins to bind. Auto parts store sell the synthetic high temp grease.