Is a certain loss of grease on my closed bearings usual?

Yes, during grease lubrication only a small quantity of grease, which gives off the necessary quantity of oil continuously for lubricating the running surfaces, is involved in the lubrication process. The remaining part of the grease, which is unnecessary for the lubrication, accumulates on the sides or leaves the bearing.

For example for applications where a high rotational speed is reached, a low filling of lubricant is enough. Here, a self-regulation takes places with the regular quantity of the lubricant. As long as the ideal lubricant content is reached, a loss of grease is possible.