How long do you want to leave your engine running un-attended is the question, try just driving off-turbo for a few minutes at the end of each run, and let it idle for 20 - 30 seconds when you stop.
think it would be a bit of a waste of money fitting a turbo timer to your engine.. unless you kill it everywhere..
Only really need one if your running some serious boost or like i said killing it everywhere.
on mine i just do exactly what Ffoxy said.. drive it not on the turbo when i know im coming to the end of my journey or let it idle for a few seconds when iv stopped or both cant hurt...