i flip mine over if they start to not spark. then, if to short ,i take it off and put another in and take them home and sharpen with my dremel tool.as for distance, others are better at that.for years i always kept my flint a knickel away from frizzen.now, i put it about 1/16 away from what i read on here.with the short hammer that was on the t/c hawkins, we used to get great use of flint with it a knickel away.but, tc redid the hammers and made them longer.so, now i put it about 1/16 away.