I've a Wusthof classic ikon knife which i've had for about 5 months, it seems to be losing it's edge. It's regularly honed with a grooved honing rod, but I'm unsure if I'm doing it correctly.   I've watched several videos on how to do this, keeping the blade at a constant angle of around 20 degrees. So, what is the norm for sharpening knives? Have I been doing it incorrectly which has resulted in the knife losing its edge, or is this normal?   Parts of the knife seem sharper than others, for instance the heel, whereas the tip seems pretty dull 
Given that the question is "how often", I want to actually answer that question, even though some of the answers above supply more complete advice.   Stainless steel knives normally want honing with a steel every 2-4 uses.  This will keep them sharp.  Carbon steel knives should be honed after each use.  If you have been honing, you should need to sharpen your knives no more than once per 1-2 years.   There are definite exceptions to this.  For example, knives used for cutting joints and bone will need sharpening and honing more frequently.  Knives used only for "soft duty" (e.g. on fruit) will need honing and sharpening much less frequently.  And serrated knives are their own special case.  The above is based on my own experience caring for 18 knives from multiple manufacturers, including both stainless and carbon steel.  Some of my knives are 25 years old and still sharp despite regular use.  So, the fact that your Wustof is getting dull despite regular honing after only 5 months indicates that something is wrong.  Possibilities include:   improper honing technique (but you seem to have made an effort there, and it's not that difficult) not honing frequently enough bad honing rod (is it a Wustof too?) bad cutting board (glass, stone and bamboo are all knife-eaters) heavy usage, like lots of boning or hard chopping   Note that honing keeps knives sharp, it doesn't sharpen them.  So if you waited 3 months to start honing, the dullness would have already set in.  If that's the case, then you'll want to get the knife sharpened, and then get into a routine of honing it every 3 times you use it. 