Cutter Question

[Faust]

What is the "normal" life expectancy of a cutter? I have a double bladed "self sharpening" cutter. My wife got it from Nat Sherman approximately 4 years ago. I have been using it steadily since that time. It has never ripped a wrapper, cuts beautifully, no problems at all (this probably will serve as the answer in itself to my question, if it ain't broke don't fix it or replace it in this instance).

I was just wondering if this was an anomoly or I should look forward to years of future use. I understand that it in part depends on how many cigars I cut with it (typically 2-3/wk on the average) and other factors can also have an effect. Any insight would be appreciated.