It's funny to see how a thread starts from a question "when to put the hands back on the TL" ends up in a discussion on when to remove the hands from the TL and from some the idea the hands should just stay off the TL.
I'll just give you my 5cts (B737) which is pretty much common idea in my company.
* TO: on the thrust levers from CLB thrust to AP ON (ATC requests immediate level off, in manual flight A/T should be disconnected and thrust reduced instantly as well)
* APP and landing: below 10000ft anytime for AT problem (1 retarding, the other not) as ground is becoming critical and identification is confusing with hands not on the throttles (it's the opposite from an engine failure, but training bias creates the idea that an engine failure is happening)