My hints and tips for rotary cutter blade changing:

Before you remove the old blade, take a sharpie permanent marker and put a big X on it.

If you buy blades in plastic 10 packs, you can store your old blades in the same pack for disposal when you have used them all (as long as you have marked the used ones) – I put mine under the new ones.   If you don’t have one of these plastic packs, find a small tin you can use for old metal sharp things (blades, needles, pins) to keep them safe for disposal – check out sweetie tins, etc. as possibilities.

Write the date you changed the blade on the new one using the sharpie marker.   You will get to know how long a blade usually lasts you, and so will be less likely to keep on using a dull blade.  Conversely, if you start having cutting issues earlier than usual, you can do things like check for double blades (yes, we will all put two in by mistake at some point), a wrongly assembled cutter (that little washer can go on the wrong way), or for a cutting mat that is full of stuck bits of threads,  before you give up on the blade.   If it is your mat that is the issue, try holding it curved while you wipe with a damp cloth – that will open up the cuts a bit and make it easier for the cloth to pick up fluff or threads.