I would consider it unethical to try and mislead the manufacturer into repairing the knife by claiming it is defective if it is not defective.
However, if you told the manufacturer the truth, that the knife has served you well for years, that it has been a valuable tool and cherished companion, that it has worn out from extensive use, and you ask them if they offer any free refurbishing services, I would see nothing wrong with that.
Who knows, maybe the manufacturer would refurbish it for free, in appreciation for a customer who values their product. Perhaps they would consider it good PR.
I had to quote this for truth.
I am a small business man and I do all manner or contracting work. I put myself in both shoes, but ultimately, and not surprisingly, vote on the side of business.
When I built my own cabinets for baths and kitchens (I do mean me!) I gave a lifetime warranty on my work. Not the finish, but construction and the hardware. I have been in business for 40+ years in the same city with the same name, so I am easy to find. I have two kinds of clients that call me for warranty issues:
!) Robert, we are having a problem with one of our cabinet doors, it won't close anymore. I remember we bought a lifetime warranty (actually included when I was building my business) and we need for you to repair a couple of the cabinet doors. OK, off I go. I get to the house and find that their children have been literally hanging on the base unit doors and swinging themselves for a few years. The client thinks it is "not good" but who can control kids these days? Go ahead and fix the doors, please. IF they were good clients while I was working for them, and if they were repeat clients, I will do it. My call, and if the wear and tear is unreasonable, then most of my clients (mostly great folks that turn into friends) will offer to pay
2) Robert, we had the grand kids over and they were using the large cabinet door as a swing and tore it off. Could we get you to fix it, we know it isn't warranty, and Grandma (you remember Ellen...) tore them up. Me - sure, I'll come buy and take a look, hopefully some new hinges and some glue will do the trick. They pay for the hinges and a service call plus a cigar and we are done.
My clients are all repeat guys and I rarely bid on work. Happy clients are referring clients in my business so I always keep that in mind. But another situation exists, not included above as these are likely no longer my clients. It is the folks that don't take care of my work (a new front door, bath cabinets, a pergola, and on an on) and they think nothing will ever wear out and they do no maintenance and use the work I have done with no consideration at all since it had a "lifetime warranty". For example, a LARGE woman that "hip checks" a door to get it open without checking to see if it is latched can probably generate about the same force as a professional hockey player on a door. Broken locksets, broken trims, cracked jambs.... should I be responsible for that? Nope, I don't care if it is a year old.
But another thing drives a mass production company like knife manufacturers. Social media, forums, websites, etc. that are frequented by fans. Would it be better to simply replace a knife, or have some enraged, entitled person rape you on Reddit, Instagram, Facebook, BF, AAPK, and on and on because you wouldn't regrind a blade or repair a handle on a knife because you valued that person as a client? Since we are a social media society (just look at the huge number of participants and even larger amount of audience here) and social media rules, it is easier to replace than to try to make up ground on social media. In fact, it is even easier still to
raise your prices on every knife so you can cover the occasional losses.
Personally, I grew up with a pocket knife in my pocket. My two oldest knives (when I owned less than 5 to my name) I still have. An old CASE "workman" from 1969, and a CASE large copperhead from 1976. Both of those knives have been faithful servants for decades. The copperhead's shield is so worn down that you can hardly read it. The once beautiful deep ruby colored scales are chocolate brown from hand sweat, cleaning agents, and grime. A couple of the rivets have their heads sheared off! I look at that kind of wear as a badge of honor, each scarring trait well earned over decades.
You couldn't get those knives away from me for love or money. I wouldn't think of sending them anywhere for any reason. Like me, they earned their wrinkles and grey hair. They make me smile every time I carry them.
Robert