I'm on the no side. I never change my plugs unless there's a problem. As long as it's running well I leave em. Then if they're in question I clean and re-gap and and still use em. Every so often I find an intermittant plug. Just changed one last week on my 70's Johnson 25hp. Couldn't figure out why it was running on one cylinder every so often (new ignition system) and changed the plug and voila...
I bought a Harbor Freight Spark Plug Sandblaster($15) about 10 years ago, never buy new plugs for outboard, chainsaws, blowers, etc. Sandblaster knocks carbon off plug center electrode insulator and other areas. Plugs don't much wear out, just get fouled. Sandblaster has paid for itself repeatedly, but you need an air compressor to operate it. Water cooled 2 stroke outboards seem to make carbon/deposits more than air cooled chainsaws and blowers, maybe high temperatures of air cooled motors burns off deposits? Good Luck!sorry to reserrect this topic but whats the best way to clean your spark plugs?