The PO of my van replaced the head gaskets (for the first time) at about
120k miles and filled the pits in the heads with JB Weld.  At around
150k, he was catching the coolant in a cat litter pan and pouring it back
in!  Then, one of the gaskets let loose (probably due to damage from the
JB weld) and it lost most of its coolant.  When I got it, it didn't leak
at all cold, but when it warmed up, wham, instant cloud of steam!  I
replaced the heads with rebuilt ones from AVP and have driven it about
15k since, without a drip.

As a comparison, my Isuzu has had two cracked heads in 130k miles.  I'd
take the waterboxer over the isuzu any day.

Bill