In WA State, if you don't show, there is no 'penalty' as such, other than not getting any refund on your original site fees. Also, if you are a no show and do not contact the SP your site is up for grabs 24 hours after your initial res date so if you happen to drop in, you might get lucky and get that site.
I know I make my camping reservations the full 9 month ahead of time allowed and have lost them within seconds of the 7am time it's open...
Anyway, after making my reservations, if something else comes up for that weekend after the fact, I will always keep my camping date.. Well, it has to be a pretty substantial sudden event to cause me to cancel, that's for sure!
So far in the last 20+ years of dealing with the reservation system, I've only canceled one time(I did cancel and was not a 'no show' about a week ahead of time)... And we still got away for the weekend, it was just a family event thing that came up and luckily was not a death or other thing.. Just a chance to visit a family member I had not seen for a long time, but have always kept in contact with since I was a kid. Love you Aunt Francis! :)
Mitch
