You can run the absolute shit out of that grinder my friend. Don't worry about the grinder.

Stripping paint is an art... It can clog disks and smear and build up at too high rpm with the wrong attachment.

I'd recommend also getting a knotted wire cup wheel and an assortment of flap discs. Welcome to the world of tool ownership and consumables. Many tools are like ink jet printers. The cost of the tool is inconsequential in the scheme of things compared to the consumables. Grinders are definitely one of those tools. I'm at the point now I just have 5 grinders dedicated to specific types of disks cause I got sick of switching between them.

Also, with that threaded Avan disk you don't need either of the arbor nuts.

Like I said in my last comment, it will be fine. These things are built to be used and abused on jobsites without ever being maintained.

The rust is nothing compared to the abrasive stone dust that's builds up when doing masonry work.

I understand wanting to take of your tools, but we only have so much time and energy available to us each day. I'd recommend putting your focus on the end product and not so much on the means. I personally buy Makita because their tools are tough and durable enough to take a beating every day and keep on going for years and years.