My self-propelled mower lasts a little over an hour on a fully charged battery. Mine is a Kobalt from Lowe's. My robotic mover also lasts around an hour on a full charge. It docks itself when it needs to be recharged. It is a Husqvarna. I saw these in action when I attended the A.S.I.A. Symposium in East Stroudsburg, PA in 2018. I was impressed by how they worked. My wife wanted me to get someone to cut the lawn. The robot was a compromise. It cuts the largest part of the year and I use the walk behind, self-propelled mower to do parts of the yard that the robot is not programmed to do. These are areas out near the street and outside of fenced in year and along the fence as the robot does not cut all the way to fence.
Ken
"The dulcimer sings a sweet song."

YAAAY! Since your dulcimer probably isn't heavier than 8 pounds, you can keep picking it up as it's obviously helped you so far, Ken! If you have a bass or otherwise heavier instrument, let it be your incentive for playing again in May.