ahhh, turbo timers that kept the engine running for a predetermined amount of time. I had turbo timers on my turbo DSMs back in the day. The exhaust manifold would literally get red hot, so yeah, shutting down the engine and letting the oil coke on the turbo shaft was a real issue.
For normal driving I wouldn't be too concerned. If you do a few WOT passes I would drive easy for a few minutes to get op temps back to normal range. Don't go for the 1/4 draggy world championship then immediately shut your engine off.