2A
From my company SOPs (and I suspect that bmi's are similar)
Select REV thrust immediately after the main wheels touch down. If runway performance is not limiting or where airport regulations restrict the use of reverse thrust, select and maintain REV IDLE until taxi speed is reached
(Benefits include increased passenger comfort, less brake wear, less environmental impact).
If the runway is short or contaminated or LVPs are in force REV MAX should be used.
Not withstanding the above, REV MAX may be used at any time the crew deem it necessary in the interests of safety.
The bit which takes some lateral thought to understand is the phrase "less brake wear". The reason this is so (we are told) is that carbon brakes work better and wear less when they are warm. Therefore it is advantageous to heat the brakes up during the landing roll and thus reduce wear!
Tried to insert the graph here but failed miserably!
What the graph shows is a steep increase in wear rate up to 100 deg and a steady decrease in wear rate above 100 deg. The proviso is that you prevent unacceptably high temperatures being reached.
EI have possibly taken a different view to bmi on this subject, because there are a number of factors to be considered. I believe that BA also have a REV Idle policy.
Hope that this helps
YS