I had a Hagon monoshocks on my old FJ. I found they lasted about 14k miles. The first was replaced and the second rebuilt both under warranty when the damping went.
It seems that road crud sticks to the rod and takes the seal out. I fitted an old inner tube to project the last one, but stopped riding it as soon as I got the GS, so I dont know if that would have solved the problem or maybe have caused the shock to overheat.
The Maxton I have on the GS has a shield inside the spring that projects the rod, so you could rig something up like that too.
Phil