We use packs on almost exclusively, however we do practice the packs off technique during line training should it be necessary for any reason one day.
As per AI instruction we turn both packs on (sequentially) after thrust reduction and in most cases the warning is thus prevented.
By using packs off there will of course be an extension of engine life (lower EGT, higher flex...yes you can flex packs off) as long as you are not performance limited. Trying to quantify those savings would, I suspect, be very hard to do and would depend on the kind of operation being undertaken.
We have just removed an engine with 6000 hrs and 12000 cycles from the wing where it had been since delivery. The only components that needed replacing were some of the first stage hp compressor blades (one of which was damaged) and was rebuilt and is ready to go back for more. Not bad life I reckon for our shorthaul kind of operation. Note that there was no turbine blade replacement which one would have expected if our engines were under undue stress.
