The work offsets are usually based on some sort of a datum (reference point) on the fixture or the part. I would think it most unusual that you would never have to change these work offsets on a regular basis. You must have some kick ass discipline in your shop
There must be some feature on the part or the fixture that you can reference to. Its difficult to say exactly what you would use, but, say for example, you run an old program and allow the program to run to position the tool beside a known edge or over a hole. Stop the program at that point, zero your operator displays, and using an edge finder, determine the distance that you have to move the machine to get the tool into correct position in X and Y. The values you get on the operator display should be the correct values for the current active work offset (sign of the values may be inverted, but that should be pretty obvious when you rerun the program and the machine goes way way off position).
The "H" offset is your tool length offsets and is not related to the work offsets in X and Y. However, there could be a Z component of the work offset, however, if your habit is to set the tools off the top of the part then the Z value for each work offset would normally be zero.