I watch ebay and stock up when I find a brand I like at a good price. I gave up on bargain blades and Harbor Freight blades..just a waste of money. I bought a new mat a few months ago and cannot believe the difference it made! I had my old Olfa mat for a good 20 years...what a difference a new mat makes!
I use my old blades to quickly cut cardboard for recycling...it's so much faster and easier than tearing it! Just use a sharpie to mark your old blades.