Firstly those multiplying diary pages. I recently bought a Filofax mini Finsbury which came with 2011 diary pages. I was about to relegate these to the scrap paper folder when I had a thought. I wonder when this yearly diary will come round again with the same days and dates. I compared it with my 2016 diary pages and was excited to note that the days and dates were exactly the same so I altered 2011 to 2016 with a black pen and now have an up to date diary in my mini. This made me think which other years were identical in days and dates so I looked it up on the great net and found this site.
Now that was funny, why wasn't 2011 exactly the same as 2016? The answer was that in between there are leap years. I was comparing the calendars in March when the days and dates lined up. If I compared them in January or February they wouldn't line up so my 2011 to 2016 calendars only match from March onwards. Not to worry, if I'd started in January I would have only had to alter 2 months of dates.
My easy answer for matching calendars is to just add 5 on to your old calendar year. The answer will give you a year that is compatible from March onwards or, if you want to be exact, go to the calendar matching site but here you could wait quite a while before your old calendar comes around again.
My easy answer is a compromise but would work if you are not too fussy.
1999 - 2004 - 2009 - 2013 - 2018
simple and no more throwing away old calendar pages.
Next those calendar pages or other pages of which you have no need. My answer to this is Washi tape. I'm not into decorating but if it saves wasting paper then I'm in.
Below is a weekly page with the lettering just covered over in tape.
I made a To Do page using this method.
Here's an address page (These pages multiply like nobody's business.)
which I've taped and white stickered over to make a Notes page.
There is hope for your old pages so give them a new lease of life and help avoid waste. Eventually these pages, once used and written over will either be archived or recycled in the compost or council paper waste.