A couple of unrelated thoughts on this thread.
First the cordless grinder. I have several of the DeWalt 18v tools including the grinder. It seems like anything that cuts (circular saw, recip saw, or the grinder) really sucks the battery, but the impact driver or drill something like that, they run forever on a charge. I thought I would use my DeWalt grinder to sharpen the mower blades. It was quite a bit slower than my corded DeWalt & Makita grinders. It only made it didn't quite make it through 1 blade before the battery was dead. I have 6 batteries, so I could have swapped batteries, but I just ended up getting the corded one out to finish the job. Incidentally DeWalt markets it as a Cut-off tool - not a grinder. When the wind blew Monica's greenhouse away, I made several cuts through the aluminum frame before the battery gave up. It is good if you only have to do a couple of minor cuts and don't want to have to drag a cord out to do it. I got mine free. Monica bought me a combo kit at Lowes. It was normally $399 and they had it on sale for $299 + a free tool by mail. I ordered the grinder/cut-off. Turns out the drill was bad on the combo so I returned. Thinking they would check the receipt for the return, I mailed the new receipt in and changed my mind and got the impact driver. Ended up getting both. The impact driver is now my favorite tool. I will never use (OK more than likely not) a cordless drill to drive a screw again. Not bad, 6 tools, 2 batteries, and a charger for $299.
As far as the truck compressor goes. Dad used to change tires for a living, he typically used a long anvil 1" drive impact wrench. When he first started working for the company he retired from, they ran compressors off the truck engine. He start in 1980 for this company, they had a '78 Chevy with a 3-speed on the tree. The odometer said less than 100k miles on it, but he figures the engine had closer to 600k. He would start the truck in the morning and it wouldn't shut off until he quit working that evening. As they started buying newer trucks, it started getting super expensive and hard to put them on the newer trucks as there was no room under the hood. They just started using the typically gas compressor in the bed of the truck. Harder to get started if it was cold and took some bed room, but other than that no drawbacks. Cheaper, easier to replace when it wore out and less wear and tear on the truck because it didn't sit and run all day. Especially duriing the summer sitting out in the field and getting it hot.