That's an interesting question, @streeter. If you sometimes overdo practice and wear your voice out too much, then a day of rest just before you gig might be better.
The truth of the matter is that if you practice regularly, and your practices are long (like a lot of yours are), then you really build up the kind of strength that will not cause you to need to "baby" your voice before a performance, except to make sure you don't do anything foolish with it.
Yes, I have made the mistake of overpracticing a day or two before a performance, but since then I have learned to pace myself every day. It is always important to pay attention to those little tickles or scratchy feelings that tell us we are hitting our cords too hard. If we learn that and even more so if we learn to avoid that behavior altogether, we can easily work out just before our gigs because we know our limitations and we take care not to exceed those limitations.
Since we are supposed to always come back the next day and clean up the cord with clean vocals after singing with distortion, that kind of eliminates the day after the gig for a day of rest. So I tend to rest on Monday or Tuesday after a weekend gig, depending on what days I performed. I do a slightly lighter workout the day before the gig. It's still the Volume 3 workout, but I just cut back the air on all of the exercises that Ken says to do so, and I can get through that workout easily, and enjoy the benefits of stretching the voice more than the average gig will require.
The key to what I'm saying, is to do enough workouts that really buff up the voice and force you to utilize support, so that doing a gig is more like a walk in the park. As you know, Ken does say that there is no such thing as singing completely without stress. It's the MANAGEMENT of stress that is important. When we truly learn to manage stress, hold back the air, and pace our voices from working out diligently, a performance is relatively easy, due to our conditioning and stamina that we have built. Another essential thing in this equation is being far enough along in the program to have learned to be aware of the voice as you are singing, and aware that you are supporting and cutting back the air AS you are performing. If you get caught up in the moment, and start singing like Superman, without using your techniques to preserve your voice, you will be like Superman when he encounters Kryptonite.
Certainly taking the day off on the day before the gig gives you that extra day to recover if you have overdone it during your workouts.
I'm sure there are lots of opinions on this.
All the Best, Luke!