[rindalir]

My solution when I lived near a museum I liked (the MFA in Boston, USA) was to get a membership and go once every week or two and only spend half an hour to an hour, in one specific room or exhibit.

When I'm visiting, I try to look a museum up ahead of time and then focus on a small but good subsection of stuff. I hit full saturation/fatigue at about two and a half hours.