I staffed a paper on the Officers' LS&GC when at MoD back in the early 90s.
Consensus then was that it was quite un-necessary, as an officer's Good Conduct was implicit. If it had not been, then the lack of the medal would show he/she had been a bad boy/girl, and advertise the fact to everyone ... not good for respect from subordinates, especially in an in-command appointment.
As for Long Service, what's special about staying in to earn a [relatively] decent pension?
I see it as a very different scenario to those officers in the Voluntary areas.