In all honesty i can say that, when in the trade, i fitted many aftermarket seals with no problems at all.
The normal reason for a quick re-leak is pitting on the steel tubes whilst I have seen oil leaking around the outside of a new seal via a deep "gouge" in the alloy slider caused by using a big screwdriver to pry out the old seals.
Now there are many different suppliers of seals and like everything else the quality will vary, whilst Honda's QC regime is supossed to be second to none (even then i have had bad genuine parts!).
Honda do use different numbers for different bikes but several have the same diameters and so will fit.
Basically if your time is cheap fit aftermarket and save some money, if you value your time fit OEM parts BUT either way make sure the tubes are good.