I rode the Oregon coast in 1992 as part of a whole west coast tour. I rode it again in 2004. It was wonderful the 2nd time around. I remembered much of it, but not so vividly that it wasn't exciting and almost brand new. I met wonderful other riders both times, which was a big part of the reason the trips were so enjoyable.
I'd ride it 2 or 3 more times without hesitation. I think it would be best with a few years separation between trips.
I guess it's a little like reading a book a 2nd or 3rd time. I really like to do that, but prefer to wait a couple of years at least between readings to make it seem a bit more "fresh".
I'd like to repeat some of my other tours too - hopefully with a family member who wasn't there the first time.