I am 59 and very active on stage, not one to stand still and play. Between that and the band not having any roadies, the best thing I can tell you is, just like working out, the day after a gig is going to hurt. It keeps you in shape. A lighter-weight bass can help, as does a wider strap.
My band (mostly Classic Rock) wanted to book two nights in a row at one point, and one guitar player and I had to veto that. We both felt that our hands wouldn't be where they needed to be on the second day. I've done two gigs in the same day, (probably 5 hours total playing time and using stage PA at the first show) and that is easier than two days in a row.