I just replace them. The cost is not that great per blade. Not worth the aggravation to try to sharpen them.

I use my rotary cutter on paper, cardstock, felt, fleece, fabric, ribbon, yarn, whatever needs to be cut. I use whatever rotary cutter I pick up at the time. I want a sharp blade with every cut no matter what I'm cutting. To keep a sharp blade using a sharpener, you have to sharpen a sharp blade to keep it sharp. A nick though and it has to be tossed or tedious time spent sharpening it back to new. DH won't sharpen a $5 blade.

I am terrible about changing the blades on mine. I don't have a sharpener. I will definitely work on getting some new blades and being more careful with this.

I sharpen mine with the blue circle sharpener I got from JoAnn's. I've never had a problem with sharpening.
I also buy my blades from Harbor Freight, they last a long time and I sharpen them before I use them because they are really for rug cutting. Sometimes the blades from Harbor Freight have nicks, but I just sharpen and they are fine.
Cost are 2 for $2, can't beat that price.
Hope this helps

Does anyone have a tip on safely separating the blades so you can replace the dull blade? They are so stuck together with the oil that it is difficult to safely separate them.

I order the Improved Cut rotary blades from Amazon.com The cost is $15.97 for 10 blades and is a Prime item. At $1.60 each, I can afford to change my blades more often.

Rather than trying to separate them, I slide the top one off, then lay it on a paper towel to absorb a little of the extra oil.

The best blades I have ever used came from eBay. I am not affiliated with them, and that is almost all I ever use eBay for.

this...I just slide them off. It's too dangerous to try to pry them off, that oil creates a suction!

I stick to buying new blades. I get mine on Amazon for a good price. I will occasionally use aluminum foil to sharpen a blade if I need to get through just a couple more things.

Also, clean your rotary cutter occasionally. That can cause skipping as well.