I use a multiple standards for "When to dump"
Now I full time.
Normally I dump every 2 weeks in teh summer every 1-2 in the winter (I use membership campgrounds so when I get to the OTHER one. I hook up and dump. tank up the fresh tank and remain hooked up. 2 weeks later when I have to switch parks I repeat the Dump/Fill and then 2 weeks later when I return.
Winters I split between membership (2weeks) and Government (1 week) and follow the same pattern. (Hook up at membership camp. dump. dump again before I leave)
One difference.. Last year when I got to South Carolina. first tank of water from Pioneer water district.. Well a change of water can,,, shall we say.. have after effects.. I went through 80 gallons in a week (normally lasts 3-4 weeks) so I dumped again.
IF the FULL light comes on DUMP
2/3 is the normal point. but anything over half is ok to dump. IF NOT full enough.. add water.