Hi Tony
It's a bit of a no brainer, one year or 3 years.
With the Tribunal ruling, as there is an end date you need to make sure you renew your PIP application before the end date, usually DWP sends out a renewal application one year before end date but not always, especially if a Tribunal has set a end date.
Gary
Nothing on this board constitutes legal advice - always consult a professional about specific problems