Previous iTunes Library - how to "force" a backup

Hi there

Running iTunes 11.4 on Windows 7 64 bit

With the Previous iTunes Library folder I notice iTunes seems to make Library backups at "random". Is there a way I can force it to do a library backup whenever I want?

Am asking as this morning opened iTunes and there was no music in it. From searching here I found the fix, that is, to copy and past a library from "Previous iTunes Library" folder to the main iTunes folder. The fix worked a treat but the only thing was the most library file was back in May of this year (2014). Henve my question.

I'd like to make this file once a month or so, is there a way to do it so if ? Is there any rhyme or reason as to when iTunes actually does it?

Many thanks

Andrew