but third-party toner for my HP ColorLaser don't seem to fade at all
Laser is fused onto the paper, it will take longer to show the effect.... you might also see the effect of paper deterioration too which is nothing to do with the toner.
Laser will probably outlast inkjet and offset in most cases.
Also, unless you are being scientific in your storage, and are certain you've got constant temperature, humidity and other storage variables in your house 24x7 (very, very unlikely) it's like trying to compare chalk and cheese.
There are other things to worry about with third party cheapo laser refills than fading.