I've made a fairly complex shaper template out of MDF and unlike many of the
templates/jigs/fixtures that I make I think Ill actually keep this one
around... Since MDF is relatively soft and is prone to damage, and swells
when it gets wet, I'm contemplating sealing it with something to both harden
it and keep incidental moisture out of it.... I am curious to know what
others have done... or don't bother to do with their "permanent" MDF
patterns to keep them in working order for the long run?

As an aside, I never thought I'd see the day that I'd be using my various
L-N spoke shaves on MDF but was delighted to find that they worked
wonderfully for getting rid of the band saw marks and removing the waste to
the line. This was done before smoothing the curves with with adhesive
backed paper on thin strips of oak. It was kind of like discovering that a
large L-N router is wonderful for getting dados to full depth after running
wavy sheet goods over a dado blade on the table saw. Who would have thought
that "old fashioned" tools would work so well with "modern" materials?!

John