One trick which really does help reduce strain on the voice is to open up the voice box when you are singing.

How it was explained to me is, to identify how to do that, you push your lower jaw a bit forward, so that the upper and the lower front teeth line up, and you open them just slightly - and just feel with your fingers how your throat and the shape changes a little. And from there you can easily learn how to do it without going through this rigmarole.

With that adjustment you can roar away for hour on hour and you don't wake up croaking the next day.