Last month I had a run of 10 day straight with a couple of doubles thrown in. The voice was undependable at best. I wasn't sure if I was worn out, getting sick or had allergies.
So, I vegetated during the day, drank warm tea with honey and lemon. Gargled white vinegar in warm water (Ugh). And before each job gargled with aspirin. I guess it helped. I made it to a 3-day break and that is what really did the trick. There is no substitute for giving your voice a rest after it has been overworked.
Eddie