Keeping your voice strong for long gigs
My apologies in advance if this has been asked before or if it's in the wrong category.
I play in a duo with my dad, and we're about to embark on our biggest gig yet. We were lucky enough to be invited to play at the Miami international boat show from February 16th to 21st, 12-6pm each day. I'm beyond thrilled to have the opportunity to do this, but I'm just a little nervous about keeping my voice strong throughout the entire gig. Typically, dad and I play 3 hour shows with no breaks. We do lots of songs together, and we've got solo ones in this mix where he'll do one, I'll do one, back and forth like that. Sometimes, at the end of those 3 hour shows, my voice will be feeling pretty tired, maybe it will even have started breaking towards the end of the night (I don't feel fatigued, but I'll go for a note and it just isn't there) when this happens I just resort to playing songs that don't take much effort or have many high notes in them. My question, to make an already long story a bit shorter, is this -- How can I keep my voice from getting fatigued and weak for 5 days of singing 4 and a half to 6 hours a day?
Thanks so much for reading my long-winded question, I appreciate any feedback. I'm still on Volume One of the program, I do the warmups before everyone of our live gigs. I try to do them lightly, I haven't erased the vocal break yet, but I go into falsetto in the warmups rather than power through on chest, just to conserve voice for the gigs. Thanks again!