Once you have learnt how to sharpen your knife and have purchased some sharpening devices, the next question is how often a knife needs to be sharpened. Here some guidance, to minimize not only the time needed for sharpening, but also the taking off of material from a knife.
Start with the paper or tomato cutting test. As long as the knife passes the test and a sheet of paper or a tomato can be cut cleanly and easily, your knife is sharp. Once this is no longer the case, the edge may just be rolled, so try stropping. A new or newly sharpened knife can be kept sharp for months just by stropping.
Once stropping can’t bring the edge back any more, some material needs to be taken off from the edge. On a whetstone, take your highest grit stone (or finest setting of your sharpener) and pull the knife over the stone in a few swipes from each side, but at a slightly wider angle than your original sharpening. This will in effect produce a Microbevel, which once sharpness fades can again be brought back for a while by stropping.
Once the time between stropping session becomes shorter, the time to produce another Microbevel becomes longer and if after sharpening, the knife doesn’t feel so sharp any more, it’s time to restore the edge angle by a sharpening session, going back to a #1000 grit or lower (or the coarse setting of your sharpener).
As a rule of thumb, in a normal household, with daily cooking and a rotation of a few knives with a blade of min. HRC60, expect to strop every week or two, to microbevel on the highest grit every 2-3 months, and to sharpen every 6-9 months. Doing so, your knife would permanently retain a paper or tomato cutting ability. The total time invested per knife into sharpening over one year would be less than 30 minutes.