Upon the first disassembly, was there any rust pitting on the caliper bore or the caliper piston? The caliper piston needs to be clean and smooth and the bore also has to be clean and smooth. any roughness will cause the piston to drag inside the caliper and its effect will show up first with the brake release.
The next area of concern is the condition of the caliper and brake pad resting surface. Over the years, they tend to wear minor grooves (or dips) in the top surface. These groves or dips will interfere with the calipers ability to "float freely" as the piston moves in and out of the caliper. If the caliper can not float freely, it may keep the brake from releasing as quickly as it should.

Both of these areas are the 1st things I look at when there is a caliper issue and the caliper has been rebuilt, and the brake hoses have been replaced. Gene