We were in Alaska in 2015 for 3 months as you we never knew when we wanted to spend more time in any place. We did call ahead in the morning we were moving to the RV park we planned to stay that night or for several. Only once did we not get a campground we wanted but did find one not that far away. Most pullouts allow overnight parking unless posted otherwise. Most SP's are not much more than large parking lots but are somewhat away from road noise. Then again most RV parks are not much more than large parking lots but often have a spectacular view. Just know how long you can go on your fresh water and how long before you need to dump and plan your paid nights to take care of that.