depends on how many "traffic/revenue" domains you have, that can support those "non-traffic/revenue" domains, when renewal fee's are due!
the goal is maintain a profitable portfolio.
but how long you hold these non-producers, under this scenerio......represents what we all must decide.
do you keep it, just because you like the way it sounds?
are you holding it for a potential buyer
is a "future forward" domain?
it is in a rare domain category? ( such as 3 or 2 letter/number com/net/org )