When I was young, I thought my Grandpa and Dad would be around forever. Seems I've felt the same mistaken way about  tools I wanted.
I found my way here on Papaws when I searched the internet about the 5910. I got directed to a 2013 post from OilyRascal. Figured I'd do my first post as a sort of reply to his.
My 5910 isn't near as pretty as his to say the least. And his is even older than mine, which was manufactured about 1981.
I'd put off buying the latest and last Milwaukee 4" belt sander. When I did try to order, production had just recently stopped. And the folks at Milwaukee told me resumption was not planned.
I picked up my 5910  a few years back and it had some issues. The lever  mechanism for changing the belt had been removed and put back entirely wrong. Once that was corrected, still  the Yoke Assembly could not be pushed back to allow for a belt to placed or removed.
There's a fella at Milwaukee; Corby, and thanks to him, his directions and detailed information allowed me to get this 5910 running.
Graphite Grease had been heavily applied to the shaft of the Yoke and had hardened like resin. It took some time before I realized this. It made the  shaft grossly oversized; preventing the yoke from moving at all, let alone withdrawing back to both reduce the length and depress the tension spring. Once I removed that and polished up the metal, everything came together.
Someone replied to OilyRascal's post that parts were no longer available. Bearings for example. Again, that was 2013 and things are no better.
I did manage to get the cork pad and the sheet metal liner. ( Attached) Also a new large tension spring for the Yoke Assembly shaft.
I believe the 5910 being heavy (that thick Aluminum Cast Housing) like someone else replied,  makes it bare down instead of going off like a runaway mule.
I show the 5910 here with the 6010 Orbital Sander, which I got before that stopped being made. They fit together real nice in this steel box that had been for a 10-1/4" saw.

The 5910 stays in the tool trailer and is a user for me.   I cannot tell you how many times I have said "Get the big belt sander out".     The only issue I have ever had from it is stretching belts when it gets hot.  I'm certain I have used it well beyond its duty rating.  The cork on mine has held up well.  The yoke assembly is a bit difficult to push back when replacing belts.  I find myself standing the belt sander forward end down and press down on it from the rear of the sander.

Ask my younger brother about whether you want the belt to get into your knee while it is running.  He has a scar.

PS:  It makes a heck of a nice onsite chisel sharpener.

Hi OilyRascal

My Grandpa was a Railroad Welder going back as far as when it was just Steam Locomotives. He'd tell about how they'd lay the back of a hand on rail car wheels to check if the bearings were running hot. A habit I reckon, I caught him doing that with the wheels on the trailer for the Aluminum boat

I learned young you could say. Soon as I ran that 5910, I was checking that front roller (Drum). It felt hot to me, but I ran the 4" Makita and that gets hot too. Still, I would like to replace those Front Drum Bearings and remove all doubt. I've been searching for a source.

You're more right than you thought about how you change the belts. That is the Milwaukee stated procedure for doing that. It's in the 5910 Manual almost word for word same as yours.

I can appreciate what you say about your brother's scar. I listen real careful for a noise change when she runs. If I hear a flapping sound I'm probably too late.

That's a good idea with how you sharpen the chisels on site