I've seen bearings that were so rusted they stopped moving and started to flatten on the exposed side, spewing metal shavings all over the crank case. I think people put way too much emphasis on exact brands of fuel. As long as you buy a quality well known brand, set the engine correctly, and use quality after-run oil you should be fine (400+ running hours). In fact, I have a few old (no longer made) engines that probably have more running time than that and still run like new! Two-stroke fuel runs four-strokes just fine, although some four-strokes like more nitro content.

Set your mixture at least every time you go out to the field. On my high performance engines I usually reset them as the temp/humidity changes even if I've already set it for the day.