Basement cold should I open vents down there

I'm not growing weed anymore in my basement after 8 years, so this question is more about lowering my gas bills. Since I'm not growing weed anymore my basement gets down to 55 degrees in the winter here in NY. My question is i have 2 vents down in the basement that kick out a bunch of heat off the furnace when its on. Do you think I should close these vents so no heat goes down into the basement or open them up all the way? I don't go down in the basement anymore since I'm not growing anymore btw.

No point in heating the basement if it’s not needed.

Most furnaces need to operate in a certain range of temp. Electronics are very sensitive to temp.
I would close one. But you should have a fresh air intake if it is a combustion based furnace. Otherwise you can get a buildup of CO.

Depends on the veg/flower colder flowering brings bigger buds but fresh air is very much needed too if in veg get humidifier an try bringing up the temp to 20 Celsius minimum temp or you may find they don’t want to grow lacking humidity an temp

Are your floors above the furnace insulated? Your basement should naturally stay 50-60f with no heat. If the floors aren't insulated any residual heat should rise through the floors. Insulating will help save gas you'd be surprised how important insulating and weatherizing the basement is.

It is a good idea if insulating you have a professional do it. They pull a blower door test on your house and make sure they don't make it too tight. Alot of states have government programs that provide financial incentive to insulate and will project future energy savings with a free energy audit