mumsgirl
At present, the Scottish Government is transferring PIP claimants when their existing claim cones up for renewal, I can't find a lead time for this at the moment I think it will depend on how easily they are managing the process at the time. If you have not been contacted then I would contact them no later than 13 weeks before the end of your current award.
The transfer will be accomplished by a review of your existing claim
but using the Scots methodology. Currently the critiera for ADP is the same as PIP. Your PIP would remain in payment until it's End Date or there is a Decision on the ADP, so it is important you keep an eye on the forum to see if queues for reassessment are building up as this could affect when you should chase them.
Again, it is not clear from the information available but I would not expect ScotGov to accept an early transfer unless you are reporting a Change of Circumstances.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems