My engine is about 6 years old. I assume it's still on the original set of HT leads. On a car engine they'd be past their best by now, possible arcing etc on damp mornings - on a boat engine in a permanently damp environment I guess this will be more serious but maybe marine HT leads are made to a much better spec to start with?
What interval does everybody change them at or just "when they start to leak"!? these are chafed slightly in a couple of places.
I found a new set of plugs in the box of bits this morning so that's one less thing I have to buy