We actually use our humidifer all year round. Even if you live in a humid area, AC or heating will strip the humidity out of the air. I have a Vornado twin tank, cool mist, humidifier and I have to fill it about once a week. The wicks should be replaced about every 4-6 months as well and a good cleaning once a year doesn't hurt either. It is capable of humidifying about 1300 sq ft. Unfortunately this model is no longer avaialable.
Check Amazon, use the OCF Amazon link and OCF will get a small percentage kicked back to them at no extra cost to you. There are also inexpensive humidity meters around. Most humidifers have multiple speed controls so at night you can use a slower setting. Our natural humidity levels are pretty good in the SF bay Area - around 68% today.

Even with the humidifier I lived with a bottle of water in my hand for quite a while post Tx. Many trips to the BR ;-)