How many times are you training per week? These are all things that are important to know.
Training to failure constantly is a great way to completely burn yourself out, especially if you're following a low carb diet.
So, regardless of how many times you train per week, I would recommend a full day refeed, and like Zach said earlier, it might even be necessary to have a carb-up meal somewhere in the middle of the week.
These are all things that you're going to have to play with. If you constantly feel lethargic and sleep quality is declining, consume more carbs during your refeeds and don't go to muscular failure so often.
It comes down to experimentation and what works best for you in your current situation.