Well, I wouldn't want dust on the eyepiece!
I've heard of people melting the reticle in their finder by forgetting to cover it
But seriously, you're putting a lot of energy through the optics, and a lot of heat can build up. If you insist on using projection, you'd better stop down your optics significantly. Better yet, solar film is cheap cheap cheap.
I was doing solar filter projection on my neighbour's fence 40m away. A 60mm aperture filter was giving a very nice eclipse shaped reflection, with no risk to my equipment