Your turbo will cool down easy.
On a summers day after sitting on 100+km/h, it'll cool from 850-900 to 400 within 3 to 4 blocks at 50km/h, even less time in winter. If you are fanging it hard around a race strip, it might take a bit longer.
If you are only doing 50-60km/h in town, I would just turn it off like any NA car [unless its a stinking hot +40 day, then 30 seconds cool down maybe??].
I've got an exhaust gauge on mine, and turbo's cool down quick all year round except for the +40 days. If you take your time parking etc then you can consider it cooled down.
Turbo's aren't working much below 3,000rpm, and this is about [depending on gearing etc]100 to 120km/h in top, they are 'on sort of' below this, but are 'idling sort of', so they don't get as hot as if they are boosting.