i grew up on the old tank metal gray cast bodied black n decker 9" and wrestled them around, we had them in our AG/Shop class and all of us abused them never saw one fail. I believe ( dont quote me tho ) that DeWalt bought the B&D rights on those and you can still get one in a plastic body. I believe they are pretty much built around that old design/specs but its not EVERY 9" they make. I have one but i cant remember the numbers on it and it seems very comparable to that B&D, a true beast, rip right out of your hand with power if you arent being careful. Run for hours grinding on things and no issues other than wear you out.
No guards on them back in that time, maybe someone removed them or not built with them at that time. They would take chunks out of your hide in an instant ( ask me how i know ) and locking the trigger was a sketchy compromise if you started getting tired or a little embellished on your grinding area.
Being a hobbyist, for the little grinders i get the cheapo $9.99 Harbor Freight units - keep one with a grinding wheel, one with a cutter wheel, one with a grinding pad. I have a 3" air cutter that gets used also so i have found for me the $9.99 ones are very much worth having. If you are running the motor down so much all the time that you are stalling or overheating it, you probably need a bigger tool for the job.
You can always put a bigger motor in anything ( binford 9000 oh oh oh ) but i dont like limiting myself to one tool. Again, all of you professionals dont mind me im just a farmer/hobby fixer as needed. I have yet to burn up a $9.99 HF Grinder and have had one of them for over 4 yrs. The other two just a couple yrs. I also have an old Chinese one that has a switch on the side and came with a set of brushes, noisy, crude and gets hot but keeps on going, gave 10 bucks for it in 1991. I dont even know where my neighbor got it, he came by one day said hey i bought these at a tool auction, want one i said how much he said 10 bucks..........ive got more than 10 bucks out of that thing for sure LOL.
I do know this, DeWalt and others make different models all the time around different specs changing minor things to save $$$ in manufacturing and support. Just like all industry, the specs can be built around a failure average on certain components so they know when they will fail. Most things ARE NOT overbuilt today. do you have a clothes dryer, washing machine or refrigerator that lasts 15 yrs now?
Safety and a litigious society have changed everything, have fun with that new Grinder!!! I wouldnt be surprised if one of these days they run time will be limited on them due to dangers of fatigue, carpel tunnel, or overworking an employee. Maybe i am being a little to facetious :laugh: