What I have heard (vaguely and informally) is:
** first 6 months: around 800 - 900 cals per day
** after 6 months: you can consider raising to 1,200
** after 9 / 12 months: raise again to 1400/1500 for maintenance
This assumes that the majority of weight loss (say 60% - 70%) will have been achieved within the first 6 months, and the slightly higher 1,200 cals a day will still lead to weight loss, but provide more nutrition. (And hopefully at 6 months out the patient will be sufficiently lighter to be much more physically active and therefore likely to be burning more calories anyway.)
This is just vaguely what I have heard / what my impression is -- obviously it will depend slightly for some people on what their starting weight is. (If they were starting at over 30 or 40 stone then upping the calorie intake after 6 months might be too soon).
Or ...... if in doubt, ask your own team, Pandora, for their own official guidelines (!).