Color photocopies are pretty stable, at least a year, perhaps longer when
light levels are controlled. The replacements are cheap, too! The size is
limited to 11x17 though.
Next best would be to find a color service bureau in your area that does
inkjet output. The process involves scanning the original into a computer
and then printing on a large inkjet printer. The images will look good, and
protected by a clear laminate last for a couple of years. Size is limited to
50" by whatever length. I recently saw an ad for a piece that was 250' long.
Cost is about $20/sq ft.
Whitney Watson
Exhibitions Designer
Missouri Historical Society