Originally Posted by JohnBurke

Pratt doesn't specify a minimum time, but it is specified on some aircraft, which is ironic; in those cases it's the airframe manufacturer making the specification, and not the engine manufacturer. I have flown aircraft which dictated in the AFM that a minimum of 15 minutes would pass between shut down and start-up, that were powered by PT6A's.

The starter limitations are very different than a limitation between shut-down and re-start.

One area that should be approached with caution are multiple short starts or start attempts, before scavenge pumps have a chance to do their work; a lot of oil can shift to places it shouldn't, and EPA cans can quickily fill, too. This can take place during several start cycles when the engine doesn't reach full speed, or during prolonged motoring.

The best cure to hot engines during quick turns is motoring the engine to cool the gas path before reintroducing fuel. One should always max motor, rather than light off the engine at the minimum Ng anyway, but if the battery is available, motor to the maximum RPM available for the starter and keep it there for a moment to cool the engine before moving the start lever. It's conducive to engine longevity and it produces more consistent, cooler starts.