The native Model Info > Statistics > Purge Unused... removes ALL unused 'things'.
My Plugin http://sketchucation.com/pluginstore?pln=PurgeAll allows you to purge all OR selected 'things'...

Hi Taipi, hi folks.

If you are going through the trouble of modelling inside wall beams to get an accurate count, dont forget that, cutting a hole is not sufficient. You must add some additional framing elements to account for the material removal caused by the hole, for example, lintel at the top of a window or door and extra studs on the sides and bottom too.

See tis page for example:

Just ideas.