Spark plugs and cap replacement interval

[KD4UPL]

I've owned my 2004 Merc Mag 350 since 2018. I've never replaced plugs, wires, or cap. It runs fine. I have no idea if the previous owner ever replaced anything either.
I was reading on several boating forums that a lot of people recommend replacing the distributor cap every year and the plugs every year or two. This seems incredible often to me.
Apparently the flat top "crab" cap I have is very problematic but I don't know that mines ever caused a problem.
The boat has about 700 hours on it. Should I be replacing these parts or just let it ride? What's the recommend interval?

 

[kd4pbs]

Perhaps just buy a set and a cap, and leave your old ones as a spare. I think in a marine environment, there’s such a wide range of service variables, which could lead to a wide range of service intervals that you’re either throwing money away or not replacing it before it fails. Only you can determine how hard you are on these items.
73!