Change to ADSL Max with router off?

[LesWT]

Demon are rolling out ADSL Max over the next few months and the
estimated date for me coincides with me being out of the country.

Being of a certain age I switch everything except the fridge and
freezer off when I am away.

My question is, what would be the consequence of the router being
off for a couple of weeks when BT make the switch?

 

[LesWT]

Thanks doran1801 and tolien for the replies much appreciated.