I've used lots of Miracle Muck for over 15 years to mount my canvas and paper inkjet prints to Gator Board. Even my oldest mounts are still attached perfectly with no sign of problems, even at the very edges.
Compared to similar glues, Muck spreads and levels very noticeably smoother and faster with the 9" foam rollers I use to spread Muck on 4 x 8 Gator Board to attach ganged-up 44 x 96 inch prints, a technique where speed is very important. That alone makes shipping Muck more than worthwhile. A recent reformulation gives Muck a much longer shelf life, I've kept some gallon jugs more than 18 months and they're still good as new with no "rotten" smell that was sometimes a problem in the past.