Activated charcoal does not hurt the cycling process one way or the other....
Use of activated charcoal is more of a personal choice than a need, however, its a good idea to always have some fresh unused activated charcoal on hand for emergency
Charcoal is a short lived product and you can't recharge it-
Charcoal/carbon come in different grades and usually will be spent in about 2-4 weeks and while leaving it in the filter shouldn't cause any problems and it can even provide more surface area for the beneficial bacteria to colonize-Once its used up and if you want to use carbon it will need to be changed per package direction.
Carbon when active-will remove odor, tannins, other discolorations, medications, some heavy metals, chlorine, some vital nutrients, minerals for plants...and so will a water change....But-if you had an accident of some type with a toxic substance that fell in the tank-adding fresh active charcoal can often save the tank along with a water change....it has saved me more than once-but I don't use or keep charcoal in my tanks all the time....not needed IMO/E.....