I always thought BIFL was about things people had had for a long, long time that was proven to last. Not, "Hey I found something I like."

Either one would probably last a long time, but you can't put off the maintenance. These engines have carburetors, and you should practice proper storage procedures if your'e going to not use them, and occasionally clean them. This is trivial and youtube makes it even easier than ever. But seriously, 90% of all lawnmowers that "break" are just because people treat them like shit and modern gas goes stale and starts gumming things up fast.