K&M works for us, because the upfront cost was zero (K&M had a drawing some 20+ years back)
One thing to bare in mind is your "lifetime" membership (plus yearly dues) is often the lifetime of the firm... Look at how many defunct membership parks there are (one large Naco/TT one near Randle springs right to mind)
There is a Thousand Trail Rd on Hood Canal that now leads to a private (family) compound.
TT has an odd situation. One company owns the parks and another owns the membership roster. They keep renewing the lease for the membership company to use the parks, but they don't have to.