oebps.log flooded by ObjectGraphWalker

When looking for errors in the log files I noticed tons of warnings about the ehcache:

pool.sizeof.SizeOf WARN - The configured limit of 1,000 object references was reached while attempting to calculate the size of the object graph. This can be avoided by adding stop points with @IgnoreSizeOf annotations. Since the CacheManger or Cache <sizeOfPolicy> elements maxDepthExceededBehavior is set to "abort", the sizing operation has stopped and the reported cache size is not accurate. If performance degradation is NOT an issue at the configured limit, raise the limit value using the CacheManager or Cache <sizeOfPolicy> elements maxDepth attribute. For more information, see the Ehcache configuration documentation.

Searching I found the following article from Progress about it: knowledgebase.progress.com/.../pool-sizeof-ObjectGraphWalker-WARN-The-configured-limit-of-1-000-object-references-was-reached-while-attempting-to-calculate-the-size-of-the-object-graph

This tries to explain with the warning means and what I could do with it. I set the maxDepth to 5000, but this too was not big enough.

So now I am wondering a few things:
- What ís a decent value for maxDepth for oebpm?
- How come the object graph gets so big so quickly? Isn't this horrible for performance? Or why shouldn't I worry about it? If anything, it's really messing up my log file.