I do not suggest that this manufacturer is correct, however fuses do wear, depending on how close to their rating they are used. Typical fast blow fuses are spec'd to carry the full current rating continuously (well almost, for more than 1 hr), and burn at 2x the current rating in about 120 seconds. If you operate a 1 amp fuse at 1 amp current for, say 30 min, you will notice the element deforming as it is close to melting. For most common fuses that don't have precious metal fuse links, this deformation occurs at high temperature and will induce oxidation in the fuse link, potentially increasing it's resistance. However, one would think that a manufacturer using gold, Pt, Ir or other PM wire would not see this effect.
And of course, to see this effect the fuse needs to run close to its rating, or even above routinely. For conservatively designed equipment running well below the fuse ratings, I doubt if the fuse "wear" would be descernable.
A common application where fuse wear is really noticable is in many older German cars (BMW, VW, Mercedes) where those open construction ceramic "bullet" fuses were common. After many years, you will see twisted and distorted elements, even though the fuse has not "blown".
And of course, to see this effect the fuse needs to run close to its rating, or even above routinely. For conservatively designed equipment running well below the fuse ratings, I doubt if the fuse "wear" would be descernable.
A common application where fuse wear is really noticable is in many older German cars (BMW, VW, Mercedes) where those open construction ceramic "bullet" fuses were common. After many years, you will see twisted and distorted elements, even though the fuse has not "blown".