I was over active in the previous 230. I changed it in the fall and again in the spring the first 3 seasons. Ha ha...primarily because I was just spending time with my boat and enjoying working on her. It isn't necessary to do it that often unless your logging more than 50hrs a year. I will follow the manual for the most part and change annually in the spring...except this year. I am at the 10 hour point and will go ahead and change the plugs/oil/filter/fog now for winter. I also keep the 1 oz to 5 gallon ratio of Marine grade Stabil in my fuel year round, as well as keep the ratio of Yamaha ring free in my gas. So at any given time, the upper and lower end of the entire engine is lubricated and protected from not only use, but for storage. After this 10 hour service, I will switch to the spring as mentioned. With exception to fogging in the fall as well as in the spring. Yamaha now says you should fog more than once a year, and it isn't just a storage thing. The properties in the fogging oil cling and do not burn off in the upper end of the engine quickly. They provide ongoing protections against moisture and corrosion, so in my mind, fogging spring and fall works good for a fresh water boat, and I would add maybe two more fogging sessions to a salt water boat that gets used year round. If I only used my salt water boat in the spring/summer/fall, I would fog 3 times, beginning/midseason/fall in those environments. If you fog according to Yamaha tech bulletin, you should not foul your plugs and you will be able to use the fogging without concern to when you do it or how it affects the plugs. Using that method, you don't kill the engine and build up a damaging coating on the electrode of the plug. The exception to this in my mind, would be if I were storing for a longer term. Such as a year or more, then I would want to use a storage oil, as well as a deeper fog, and putting the engine back in service after would require a good deal of work and cleaning.