At around 40-50g o carbs a day the ketostyx will stop reading just because that is there limit. So you can still be in ketosis at those high levels.

Basically Atkins states Ketosis is for induiton and OWL. By the time you reach premaintannace though you should get out of ketosis since you are no longer trying to lose the weight, just get into maintaining it. It is also so you can learn how to cope with eating without the appitite supression of ketosis. Kind of like having to take responsibility without the aid becoming a crutch