My guarantee for 27 years of mold making is "Not more than .0015 over specified diameter, not less than specified diameter." I require the alloy to be named, but heat you cast at makes no difference, as the alloy solidifies at one temperature. I need a bit of rope to run with on weight, because of variables which go crazy with alloy and diameter changes, but give me a range you'll be happy with, say 5% of bullet weight for acceptable range and I'll guarantee that too. in other words, if the desired weight is 300 gr, 5% would be 15 grains. If 300 grains is the minimum weight acceptable, I'll aim a bit over, if 300 is max, I'll aim a bit under.
I don't date my guarantee, because the fact of whether I screwed up or not doesn't change with time. So, if you break your casting finger or get a heart attack or have to live through a mother in law visit, or for whatever reason don't learn the mold is faulty for some time after receiving it, I still make it right. 10 years is the longest time i've covered a mold so far, but that isn't the limit..
I brag that my molds are the best, and see to it that you think so. Quality is the only way I know of to convince customers of it.