Personally I find FoF to be a cramped, uncomfortable mess. Granted, its design was cool 30 years ago and still is. The concept of a magnetic launch combined with an indoor experience is very, very cool. I do not however, consider it part of KD's core like I do Rebel Yell (Racer), Eiffel Tower, I305.
At the end of the day, it's a machine. Kings Dominion wouldn't owe us a thing if it one day was simply done and they decided to use the land for other things. One day FoF and I305 are going to reach the same question just like Nessie did, do we refurbish, or do we scrap? Besides routine maintenance, capital projects are what keep rides alive like that and the research does get done. They count every last person that enters each ride's queue. Nessie got the attention because it still gets the numbers. Flight of Fear's day is coming when one large expenditure will raise the question and they're going to look at budget first, then popularity.
Which is also why Volcano was not salvageable. While popular, it was WAY too much money and time to fix what was going on with that thing.