You won't know until you've done your first one. You do what works for your personality.
As standard, I have a week of literally eating all the cr@p I can get my hands on (normally a week is too long for me though, I can pile on 1st plus water on that time) then get into off-season mode.
For me, my off-season, in the past has been increasing carbs by 100g a day more from whatever I STARTED dieting on, and increasing protein by about 50g a day.
This year, I've gotten it down to a T now, keep increasing until you maintain and push it as far as you can without gaining massive amounts. Pick a weight you're comfy with and try to stick with that.
As for treats - I have them as and when I want (normally once a week except time of the month when I have about 3 days of sporadic snacking).
But that's me.
My advice is simple - roll with it

Have some time to relax, let your body adjust, recover, enjoy some nice grub. Only worry about your food intake IF it all starts going Pete Tong. If you're obsessive/too strict all year, your body won't respond as well to dieting next year IMO. ENJOY THE REST!
You can afford to gain a bit more weight than I do as a) you diet well and b) want to gain more muscle.