JCKT makes good points about use. I'm posting to point out that interchangeable blades aren't the only way to guarantee a hair-popping edge. When that blade is reserved for emergency use, it's not losing the edge you stored it with. My Al Mar Payara is razor sharp at all times for this reason.
The moral: if you're designating an emergency blade, interchangeable or emergency-only designation are two things to consider.
The moral: if you're designating an emergency blade, interchangeable or emergency-only designation are two things to consider.