Sameness and longevity of design. In this counrty there are thousandds of stunnning development style boats that are no longer competitive and so are worth nothing and no longer "useful". I have just bought a very sound R class for the price of dinner out for two and will make it into a sailing skiff. I will sell the rig etc for more than I paid for the boat. The sailor of this sort of boat often stays with it and slowly drops out of the "respect" of the faster, newer boats and in the end and is no longer on the beach to welocme newbies and fill out the fleet while having the experience to push near top sailors to better things.
The Paper Tiger is an example of a boat that just keeps on keeping on delivering great competition and technicaly demanding sailing style. The fact the chap who buys a fagged out H16 can see himself in a champions boat for less than a tenth of the price allows a heap of new start ups in the class financially.
Which is the best sports car in the World? Porche 911. How long has it stuck with its basic design... forever.
Not what a formular style class wants to hear but to ignoring that truth does ot help understand the answer.
What will be very important to a formular style of boat is that the formualr IS NOT changed to accommddate new fashions. Like Americas cup all of the boats over 15 years will start to be essentially the same so long as rules are not changed. Should F18 have a lighter weight restriction? Tomorrow morning if they are going to do it or never. The day they do it the present fleet dies. Manufacturers hopefully understand why Hobie is so successful and won't go for short term gains.

C class by the way is hugely successful as a formular to create great strides in tech ect but hopeless from a class for group participation perspective. It can only just stay on the radar as far as that is concerned. I predict three to four years of heated competition and then a three million dollar 25 foot beach cat will let everyone else racing is over for another decade.