The variable nobody mentions in the frequency arguments is which ink is in the pen, and it changes the answer by an order of magnitude.
Roughly, from least to most demanding:
Ordinary dye-based inks from the major makers. Well behaved, designed to be forgiving. A pen with one of these in constant use can go a long time between cleanings.
Heavily saturated and shimmering inks. Shimmer is suspended particles, and particles settle in narrow channels. These want cleaning more often and want the pen used regularly, or the particles have time to settle where you cannot reach.
Iron gall and pigmented inks. These are the ones that punish neglect. Flush promptly, do not leave them sitting unused for long, and follow the maker's guidance rather than general advice.
Anything unusual — home-mixed, very old, or a brand nobody discusses — treat as demanding until proven otherwise.
Which also answers your six-pen situation: you probably do not need to treat them all the same. The one with the plain dye ink you use daily can wait. If any of them has something shimmering or pigmented in it, that is the one to do this week.
And the single habit that prevents most of this: do not leave a pen inked and unused for months. Ink left to dry slowly is what causes the problems people then need aggressive cleaning to fix. If a pen is going into a drawer, empty it first.