There seems to be a bit of unwarranted consternation about the durability of RMK supplied sheaths in the field. Rest assured, there are plenty of extant examples from WWII that served in the both the European and Pacific theaters that remain in good serviciable condition. Same for Korea and Viet Nam.

While waxing a sheath can greatly reduce the chance of "rotting", it is not necessary and was originally used for the #16 to combat the ravages of extended saltwater immersion.

Generally most have put a typical leather treatment that is more than sufficient relative to the longevity of the sheath in service and beyond, and there are better treatments currently available than were in the past. A little maintenance can go a long way for a user.

I would caution though on treating vintage sheaths at all. Many have the misconception that every sheath acquired needs some type of treatment. In many cases, it can reduce the collectibility and value on a knife/sheath.

Not everything requires an "aftermarket" upgrade.