Being 58 years old, this is what I have done:
1) Changed from a 34-inch bass to a 33-inch bass to alleviate tension on the strings and give relief to how much I have to spread my fretting hand to properly fret the "cash register" (my left index and pinky are both starting to curve in, so I don't have the reach I used to);
2) Made sure the new bass had a proper back of the neck profile as well as crown radius and rounded edges so I could adjust my left hand depending on how it feels during the evening, including (gasp) relaxing in a "fence post" grip if need be to give rest to the thumb and injuries from an old dislocation injury;
3) Lighten the weight overall of the bass so there is less shoulder and back stress;
4) Wider leather strap to help avoid any nerve pinching in the fretting arm or hand;
5) Changed from traditional strings to "balanced tension" strings so that it feels comfortable from string-to-string; BT sets tend to have slightly lighter gauges on the D and A strings than traditional sets.
6) Consulting some teaching friends of mine to make sure my posture and technique are efficient and that I haven't acquired any bad habits (other than the occasional "fencepost" to give my left thumb a rest) that would decrease efficiency and actually make matters worse;
7) Changing to lighter amplifiers and speakers that have the more efficient "Class D" circuitry and Neo speakers, and installing casters on those larger cabs that do not already have them;
8) Asking for help when lifting equipment from floor to stage to take stress off everything from hands to back;
9) Most important: maintaining a healthy attitude of staying relaxed and having fun at gigs, since I still get to rock gigs on a regular basis, including locally and regionally, including bars, corporate events, fundraisers for the regional symphony and opera, concerts in Mexico for the Sister City to where I live and in Zihua to raise money for the schools, and in Japan for the Sister Cities cultural exchange, among others, and including helping youth learn to play.