Your muscles will recover a lot quicker if you take the occasional day off. If you want to row some fast pieces, two or three or even four days off will put some real snap in your stroke when you return. Conversely, if you try for a 5K PR, for example, expect not to be at your best the next day.
Well I'm still trying to build a base. I feel like a slacker if I take time off, even if it is the intelligent thing to do.
I hope I will be ready for fast pieces later this month or next. Most of my PRs have been set in January and February.