All my rolling stock have axle boxes that use sealed stainless bearings. My logic has been and still it that if you lower rolling resistance you can pull more cars with the same effort. The only down side is wheel blocks or brakes are required on rolling stock left on a siding as even the wind will push them along. Here are some of the rolling stock items that have bearings built into them. They work better than ever expected.
The Pechot bogies were my first test with sealed bearings (same as the RC cars use - I have bought several lots over the years directly from China). I first tested the Pechot Bogies by leaving a pair out all winter and summer on the track and come spring they still ran as though they were brand new. I was able to get them to go almost completely around the track by giving them one push. They would have gone further if it were not for the speed factor in the corners.
The pic below is the Pechot bogie showing the resin castings with the bearings inserted. All are in 7/8n2 scale . (1:13.7) for G gauge track. The last two pics are of a current project that is almost complete (will start a new topic on the build once it is finished, in about two weeks). The last two are of a Darjeeling Tea Van in 7/8n2 scale. The teavan is a accurate as research would allow. I have all the cad files available for download on my site ( see footer). The idea of this project was to make it an exact replica of the original. For the axle boxes I designed them in cad based on every photo I could find of them, then a highly talented man by the name of Today Montgomery machined the molds and they are cast in white metal or zinc. The axle boxes use the sealed stainless bearings and the leaf springs are full working springs with a tension set for its weight and proper motion. This one will also have fully working brakes which is really all that is left to complete on the model. That is one of the reasons I love 7/8ths so much, being near doll house size there is little to no excuse to make something work or adding a detail.