Ok...the fuel leak saga continues.
O rings and such do have a finite lifespan. The ones on 2K4S have a 15 year (196,000mi) life.
More fuel filter canister leaks, condensed story:
Replaced the O ring on the block off plate for the optional fuel heater, the water in fuel sensor and the sealing washers for the fuel in and out banjos. Leak free as I can be, at least for now.