This is just question from a newly qualified TCAS pilot.
I thought that the whole TCAS event takes less than 60seconds from intial traffic traffic to the event finishing.
If your high up and already got the rubber jungle out in the back and the crew are on O2 surely the addition of 60secs isn't going to effect the safety of the decent. In fact if your going down like a bat into hell. I would suspect that you will be given a decent rate TCAS which will still have you going down but just not as fast.
Seems strange that you would turn a quite important peice of safety equipment off, in fact your only one for avoiding collision. When you have another emergency when your attention will be diverted away from maintaining your SA.
As I said this is just my thoughts and please educate me if i have got my head round the TCAS thing the wrong way.
Summary is that my risk assement is that the additional risk of fatal outcome is higher with the TCAS mode downgraded than the additional risk of the emergency decent profile being not the optimal one.
MJ