If you only use one, the simple answer is that you have everything in one place, no worries about duplication or forgetting to copy information from one to the other.
In the past, I tried to use more than one organiser a smaller one to carry with me and an A5 at home. The mistake I made was to have diary inserts in both of them. Keeping both up to date became quite a chore.
If you also keep a digital calendar up to date as well for work or family reasons then keeping everything in sync becomes a bit of a headache, especially if there is a difference in the information recorded... which one is correct!!
A variation on using more than one organiser is where you have something like a slimline for your diary insert and a few notes/information pages and a larger personal size which contains the rest of your pages that you might not need access to immediately.
This works and you can duplicate the information pages. It is the duplication of pages you are entering information on to that needs to be avoided (diary, to-do lists, etc).
If your additional organiser(s) contain completely different information, but it's just an easy way of storing the pages then that's fine. You might have an organiser dedicated to health or a hobby. I have known some people split work and personal but you can get back in to trying to maintain two diaries with that set up.
What is your experience of using more than one organiser on a regular basis?
