I think you should clarify when you feel your products are not working the way they used to. I tend to be a clarify every week girl because I like
the squeaky clean before my usual overnight DC. But, I usually only wash/condition/moisturize/seal my hair once a week (you may not do this because you refresh the TWA during the week, I know I did when I was at that length). The rest of the week I leave it alone if I was heavy on the moisturizer and sealant, otherwise I throw some light leave-in or mist on during the week (which can cause build up that needs to be clarified, IMO).
So it is really up to you, but when tried and true products start failing on you, I think clarifying is a good first step before considering a protein or other type of treatment.