I would not do this or any other thing to the heads as "preventive
maintenance".  My motto is the old "If it aint broke don't fix it!"  Yes I do
other PM stuff like oil, filters, tune-ups, etc. but with the heads; if
they're not leaking why rip them apart?
They will probably leak soon enough or you could be one of the few that gets
200k miles before having problems.  When they leak then you can worry about
repairing them.
Thats my 2 cents.
Ken Wilford
John 3:16
PS God forbid that you should spend time and money fixing non-leaking heads
only to have the problem crop up in another 20k miles 'cause the JB weld ate
your gaskets.