When I had a shop we ran a $$ special on System Brake fluid Flush--this was in the 90's. The majority of older rear or both F & R drum brakes would bring their personal collectable vehicles in for the brake flush special. some were almost 20 yrs old. We would do the complete system brake flush. Probably 50% of them returned within 3 months with leaking brake cylinders, or calipers, or master cyclers with a bypass problems. Kind of reminded me of replacing a water heater in an old rental home I had. Mess with old plumbing & the last thing to replace was the water line coming into the house. Sometimes delayed maintenance can get expensive. I don't have a questimate as to how many years or miles on the Spyder are required to avoid the old plumbing issues....I would hope 5 yrs should be safe.
Dot 3 sucks,Dot 4 is much better & can be used with anti-lock brake systems--both dot 3 & dot 4 absorb moister, Dot 5 is the best--doesn't absorb moisture but is Not suited for anti-lock brake systems, use Dot 4 best for the Spyder
Darrell