People seem to accept using up a 10$ grinding wheel but pizz themselves if they got to replace an 8$ bit. They do and can last a long while but to me they are replaceable if needed. Sometimes putting a dollar or 2 per big ole hole is rather insignificant.
I wrecked a 4 inch the other day on of all things a piece of light alum sheet, ripped the teeth right off.
Old **** oil is so messy, A few drops of rapid tap or tap magic is ideal and needs just a pinch per 1/8 of steel and on most occasions I simply use water. Sawed 2 holes in 1/2 plate the other day, did it with water and about a minute or so a piece.