I bought a pallet of HF returns about 10 years back. Took the parts and rebuilt 2 complete saws plus leftover parts. Sold one saw (for the cost of the pallet plus extra), and kept the other, which I still use to this day. In both, I cleaned out the gearboxes using kerosene and replaced the oil with 90W gear oil, same as I use in my car. Never had a problem.

I get blades made from the leftover pieces of stock they use to make bands here at work. Starrett bimetal, which they buy in large rolls. Since they cut stainless steel and solid nickel here, they go through a lot of blades, so I get a new blade about once every six to nine months. I think I have 3 replacements stacked up, because I mostly cut aluminum and brass. But if I even suspect it's getting dull, I swap them out and return the old ones to work for recycling.