If you look in the owners manual, look for the recommended time/hours to check the valve lash.I think that is definitely something to look into though I only have 60 hrs on the machine, I literally only use it around my yard. Would that be something that would all of a sudden cause the engine not to start?
Then a lot of start/stopping usage without blowing the cobs out and building engine heat will slightly foul the plug. These are low compression, low output engines so small changes cause problems.
On my bike at 60 hours I would have been around 600 miles, with several heat cycles on the engine and this causes any valve stem stretching.
Based upon the thread title, something has changed and I would check the valves and install a new plug. Then once you get this figured out blow the cobs out every week or two on a good long day ride.