Aprox 1/2 hr a day for 3 years. I have tried to keep the integrity high, for eg, if listed as EF and is clearly only aVF say, I do not record the price realised for either aVF or EF. In this case the coin normally realises a much higher than book for aVF coin, so price is affected by misinformation. I also cut out the ones that may be correct grade, but have a overly detracting feature such as scratches, spots and the like. There are exceptions ,for eg, a VF 1927 penny( book $16.00, but lucky to get $4.00 at auction), but even at a half grade above, say Good VF, they tend to fit into the percentages above.