I have 2 John Deere General steam engine sets and 2 Polar Express Steam engine sets that I took to train shows to run. The D cell batteries would last about 3-5 hours running most of the time with the kids controlling the trains with the LionChief remotes mounted on the fence for the kids to use, really depends on the quality of the battery if you spend more you generally get a longer lasting battery.
What I did to save $ on batteries was to take out the D cell battery trays and cut them up to fit and wire in a 8 AA cell battery tray or 2 pairs of AA 4 cell trays depending on the battery tray shape. Then I used Ikea AA rechargeable batteries 2450 mAh 1.2 volt. https://www.ikea.com/us/en/p/l...06-aa-1-2v-50504692/
1.2 volt x 8 = 9.6 volts equivalent of the 6x1.5 volt D cells. I found that these would run for about 4-5 hours. This particular battery has a very good rating for long life and repeated charging and high power storage. I have run this set up for a several train shows Christmas and regular shows in the past and the Grandkids still use the trains once in a while.