Well...I have multiple Parkers that are over 100 years old and they haven't worn out yet so I don't think wear is an issue. One is over 120 years old in fact and it still works.
All gun makers have been in trouble at one time or another - but Lefever was shaky during the heyday of gunmaking. That would be like an oil company in today's world having trouble making ends meet. Being a gunmaker means being a businessman as well, sadly enough. His offering unto the market lacked stability, aesthetics, continuity, and an effective sales plan.
I don't care if Parker made most of their money on toothpicks and flavored condoms. What they did was turn out the finest American shotgun ever made. Time has proven that. If Uncle Dan was so great a gunmaker, why did a coffee grinder gun beat him out then and now?
