Whether we are on hook ups or using tank we go a week before dumping.
50 gallons black & 78 gallons grey.
I do have to shuttle some grey over to black at day 5.
OP....
My problem(s) with a 'holding tank' is having it slid under my RV. I'm sure it will fit but not to thrilled with the idea of it venting under my rig and around the sitting area outside.
Bad enough when some CGs have neighbors sewer hookup right in your yard but venting is done with a 8'-10' stand pipe with elbow.
300 gallons should be roughly twice monthly pump out ie: $40/month