Personally no,I think they're a complete waste of time. But some people will disagree. I dont think there is any evidence to support their use today, in the 80's perhaps where oil quality and turbo design was far far inferior than right now. The principal is to allow the car to idle for a period of time to ensure the bearings have a continuous supply of oil (as turning off the engine will stop the flow even though its still spinning) and more importantly, stops coking which happens from stagnent oil sitting in a pink hot turbine.
If you've been pulling a heavy load for a while up a hill where its on maximum boost then the car will need to idle down. How often does one drive lke this and need to pull over and instantly turn the engine off??? Never. In the real world, you'll coast slowly into a town or road which is almost always sufficient. People are changing their oils every 30sec these days as well which further negates the need.
To my knowledge the TD42Ti turbo is oil cooled Not water cooled as in series 1,2. They also dont have bearings as such, but bushes. So I would take note of the EGT's when pulling up(mine can be as high as 300+) at anything above 150c I wont turn off.