I don't add anything for storage, I just fill it with fresh gas before its long winter nap. During the winter I also use that gas by siphoning it off periodically for power tools (leaf blower, snow plow, chainsaw).

In the case I described here, I found the crud in the carburetor early in the season. In other years, I haven't noticed the symptoms until later, sometimes mid-summer. Mostly, though it is after a long period of dis-use.