Not very often can I help on this forum, but here is the skinny on "flat spots".
Temporary flat spots were a tire problem many years ago when everyone ran bias-ply tires. The only way a radial can develp a temporary flat spot is when the vehicle is parked after a period of high-speed driving which results in high tire temperatures. Without a period of low-speed driving before parking the vehicle, the temporary flat spots can develop.
But don't worry, temporary flat spots can be removed by driving a distance of at least
15 miles at speeds of at least 55 mph to heat the tires. If the wheels and tires
are to be balanced, the driving session should end with slower driving to allow
the tires to cool down while still rolling. Remove the wheels immediately
for balancing.
Sorry if it sounds like a canned statement, my fa-shure is a tire nut for the past 40 years...
If you still don't believe me, the boat takes over 3 weeks from Europe to the East coast and nobody rotated your tires on the trip over...
Oh, and the shelf life of regular unleaded is 30 days, super/premium could be up to 45 days, AVGAS is best, 6 months before any worries.
Peace!
Krafty