Getmeupthere, you seem to say that none of us knows [what we are talking about] of the rules in tablets of stone.
The first thing you need to remember is that Flexibility is the key to air power. Then the general services one, Hurry up and wait, and the final one, more usually applied to self-loading freight, Time to spare go by air.
Then the thing you learn as you start your second tour is Never believe what the poster tells you UNLESS his tourex date is AFTER yours.
Big Unit Specialist, apart from my Son in Law being in the RAF Regt, and daughter too! There have also been RAF Regt cross-overs too.
As a young un you may not recall AN who switched from, I think Fg Off, after one tour to nav training. He was stn cdr at Kinloss I believe and last I heard was an Air Cdre. Could be higher now.
See your PM BUS