I cannot answer why '3 months', if indeed that is the case - I do not know. I do know that it is done normally to go somewhere where there are bluer skies so the team can put things together with more weather reliability. You can practice just so many 'flatties' and 'rolling' (if you are lucky!) before you need a 'fullie'.
In my time there were fairly stringent financial restraints which precluded travel 'abroad'
. Cyprus has been a favourite for a while. A session out there is far more productive in 'getting ready' than watching the rain drip down the windows in the UK.