My doc told me one a day was probably a positive, 2 a day he thought was neutral, and more than that was starting to get bad.
I think that's about right, which doesn't mean I do it. We have all sorts of "recommendations" for this and that, no many of "us" follow all of them, or even know they exist.
I mean, it's ILLEGAL to drive over 70 on most freeways, not just a recommendation. Around here, that'll get you run over unless you're in the right lane and/or traffic is clogged. I try and hit the median speed when on a freeway.