Old topic - but may be new to some members -
 

Some things really do get worn out and it makes sense to replace them:

Some things that I have had to - reluctantly - replace - because they were dull, warped, or otherwise non-conducive to accurate cuts or easy sewing.

Gouged cutting mats - if used a lot - no matter what they brand - they will show that they have been used
Dull blades - if your table knives are sharper than your rotary blade - maybe time to change it?
Dull needles - I really don't mind hand sewing with a slightly curved one - didn't reaiize how dull it was until I started using a new one - the sewing machine does NOT like a bent needle!!l
Worn out ankles to the presser feet - had one that the foot kept falling off of - new ankle took care of that.
Iron that spits or temperature control has gotten wonky
Dull seam rippers
Rulers that had curves worn in them from being used so much - no wonder the cuts were uneven!
Scissors that need sharpening - if Ginghers - send them to the Gingher place
Needles or pins that are dull or have a burr on them- or have gotten rusty - the rust will stain your fabric.
Check to make sure your bobbins are still round. Occasionally one of mine has gotten stepped on or the cat thought it was a toy.
Can/does sewing machine oil go bad? I have some that must be 50 years old.

Check ebay for rotary cutter blade deals and sewing machine needles. I purchased some blades from 123sewinglights (I think) - and they were good.

If the machine oil has a yellow or gold color it is too old to use. Machine oil should be clear. Machine oil is made to evaporate so that's why it's important to keep the machine oiled. If using oil not made for sewing machines, it will not evaporate, gets old and sticky and causes all kinds of problems.

I knew to use ONLY sewing machine oils - I did not know it was supposed to evaporate.

Interesting info about the oil. I knew about the color, too, but didn't realize that it was suppose to evaporate. Now this makes sense about my mom's Necchi machine. The inside of the machine was so gunky that it wouldn't run. A machine repairman had to pull it all apart and soak the parts in some kind of cleaner to get it working again. My mom loved the machine and I learned on it. It was like an Italian race car, it sewed really, really fast. Love it.

good to know about the oil color.

I think most of us has had to face discarding some of these items. Great topic

Yes, I know some things must be replaced. I have replaced most of the things you mentioned.

I'm guilty of having a dull seam ripper and I also try to get just "one more cut" from that poor old rotary blade. when I replace these items I'm in awe of how much better they work.

socks and underwear.

I recently took a good look at my rulers and am in the process of replacing some. You really can bite into them some over time and then I have a few that have been knocked around and the corners are starting to go.