My daughter's boyfriend insists on running dehumdifier on continously, even at this time of year. will it dry out wood trim and oak flooring and damage it?

Since I have no idea of the location, the climate, or the type of construction of the house I have no idea if it is needed or not.

But the only way to know is to measure the RH in the house.

Bill is correct.

Here in the Boston area, the last two days have been very muggy and the RH was very high, so a lot of people are still using dehumidifiers.

BTW, RH is Relative Humidity

This picture is of a meter that measures RH. We took this picture two days ago on a job site in Newton, MA.