There are those who advocate that cycling carbs is ok. That exception is really for extreme athletes who burn off those carbs within hours or even minutes in extreme cases. They can basically be back into ketosis in a matter of hours or less. Most of us are not extreme athletes, so it serves no purpose.
I do compare it to alcohol… alcoholics know not to drink… ever. Carbs are more addictive that alcohol.
Some alcoholics call themselves “social drinkers”… and some people just have drinking problems but they’re high functioning… carbs drive insulin and glucose and prolonged exposure will cause health destructive effects - only you can decide how much disease you’re ok with.
But as with alcohol, falling off the wagon isn’t the end of the world. You just need to learn from it and cope better.
The good news is that once you’re fat adapted, the body will recover faster and faster. It will become metabolically flexible and quickly switch to oxidizing fat for fuel as soon as it can.
I had a family member cheat for one event and within hours her inflammation came back with a vengeance. She was in pain after feeling the relief of Keto… my advice was to fast and exercise to purge the excess glucose as fast as possible… and then she was fine.
Just got to get the bad chemicals out.