@Jimm - how much I monitor depends on whether I am waiting for something on my machine (like a metadata download)...
I'm not likely to add such a parameter. Count Pages is a job which runs in the background of calibre, just like downloading metadata. At the point that it has the information ready to update your books, it *must* have exclusive control of the calibre database. Imagine if you were allowed to be editing one of those books while calibre is also trying to update the database for those books - you have the whole "hell" of concurrency and stale data to deal with.
You have to suck it up and live with it basically