My lip is bleeding as I type this, and I went old blade today. I was also not paying attention, though...

you don't really need to refresh blades if you're going for a post-4 day shave the old one should be good enough..

but I also just get a barber to shave it off if it's been 5days+, like I can't be bothered

Heh, I shave once a week. It's not because I don't grow much hair, it's because I don't really like shaving every day, and there are a number of folks with short to scruffy beards, so no one seems to mind. I use the same blade for a few months, given that I only shave once a week. My razor has a little lotion strip, and once that wears down, I'll change the blade soon after.

I'd say fresh is definitely better: the more it's used, the blunter it gets.

I wrote up several shaving experiments a while back.

I like a fresh blade with no water of shaving cream and an old(er) blade with water/shaving cream.

Depends on what kind of razor, imho. I recently switched to a DE Safety razor wet shaving regimen, and I shave every day, with a fairly light beard growth.

I personally suggest, cartridge or safety razor regimen notwithstanding, that you definitely go with a new blade/cartridge. Old blades (especially cartridges) pull and dig into your face enough to turn your morning shave into a Bataan Death March.

Why not give your mug some love and use a sharp blade? Definite bonus points for switching to a safety razor regimen - WAY, WAY WAY better for your skin than cartridge shaving, zero ingrown hairs, and environmentally far superior than catering to some asshat Gillette marketing scheme about "shaving systems."

If we're talking double-edged safety razors, fresh blade, imo. The blades are sharpened really finely, and any introduction of rust from moister that might accumulate will dull the blade more than I'm comfortable with. The old-unused blade won't be as dull as after a full shave, but dull enough to not have that nice crisp edge that slides across your Adam's apple without impediment. Especially with 3-4 day old stubble.

Always a new blade for old stubble.

Fresh blade is always better but if you use an old fashioned safety razor you can refresh the blade by running it through a cork a few times.