In older engines of all brands I would agree with Mike. The later engines, especially the newer design MB engines of the last fifteen or twenty years can take several valve, or top end jobs before it is necessary to attend to the bores, rings and pistons.
Used to, especially with engines under load such as trucks, you would sometimes lose cylinder integrity before the valves.
There was an article about this a few issues ago in the Star magazine. They confirmed what my opinion has changed to in recent years regarding this.
It is easy to determine the cylinder integrity before disassembly. Do a compression check, then squirt oil in the cylinders. Do a second compression check. If the compression increases, the cylinder integrity is responsible for the compression loss and probably also needs attention.
Have a great weekend,