The strange thing about knife durability
A knife wears out by being maintained. Every sharpening removes steel; eventually there is not enough blade left. The thing that keeps it working is the thing that consumes it.
That is why the sharpening service is a more interesting question here than the warranty, and why one program stands out.
LifeSharp is the outlier
Benchmade’s LifeSharp program re-sharpens a knife to a factory edge free, for the life of the knife - and includes cleaning, oiling, full inspection, hardware adjustment and a tune-up of the deployment and lockup. Benchmade covers return shipping; you pay to send it in.
That is a genuine service program rather than a replacement scheme. The same knife comes back, adjusted and sharp, which over twenty years is worth considerably more than a warranty against defects.
The warranties
Spyderco warrants genuine products free from defects in material and workmanship for the life of the product. Loss, theft, accidents, abuse, misuse, improper handling, alterations, neglect, improper sharpening, normal wear and unauthorized repairs are excluded.
Buck - Forever Warranty. Each knife free of defects in material and workmanship for the life of the knife. Normal wear, misuse and modifications are excluded - but the company states its repair department can analyze and repair misuse damage for a reasonable fee, which is a repair path almost no competitor offers.
Opinel publishes a lifetime warranty with exchange for defects in materials and workmanship, on a knife costing under twenty dollars.
Victorinox publishes a lifetime guarantee against defects, excluding misuse.
Steel, and the sharpening trade
S30V and S45VN hold an edge for a long time and take real effort and proper abrasives to bring back. Excellent if you send knives away to be sharpened; frustrating if you use a stone at the kitchen table.
VG-10 holds a good edge and comes back easily on any stone.
420HC dulls faster and sharpens on almost anything, which is why Buck has used it for decades on a knife people take hunting.
XC90 carbon steel on the Opinel takes the finest edge of any steel here and rusts if you put it away wet. That is maintenance, not a defect.
The super steels are not automatically the right answer. An easier steel you actually keep sharp cuts better than a harder steel you have given up on.
Locks
Compression lock (Spyderco) closes with your fingers clear of the blade path, which is the safest one-handed design here.
AXIS lock (Benchmade) is ambidextrous, strong and smooth.
Back lock (Delica, Buck 110) is extremely strong and needs two hands to close safely.
Virobloc collar (Opinel) is a twist ring that locks the blade open or closed - simple, effective and a hundred and thirty years old.
The thing that ends knives
Not wear. Loss. A knife carried daily for twenty years is far more likely to be left on a train than to be sharpened away.
Which is a genuine argument for the Opinel at the bottom of this page: at under twenty dollars with a lifetime warranty, losing it is annoying rather than painful - and it cuts beautifully.
