The pills should only be taken every 2 or 3 nights as needed. They are not meant to be taken every night. It should be the lowest possible dose needed in order to do some good. For example, drugs with long half-lives stay in your system longer and could still be in your body during the next day. This is not uncommon in the case of sleeping pills.
Some people complain of feeling worse the next day, as though they have a hangover.
Drugs with shorter half-lives on the other hand are gone from your body by the morning and therefore, do not have the same effect on daytime functioning. The drawback with these drugs however is that after a few nights they can make insomnia worse once you stop taking them or they can cause you to have insomnia in the early morning hours. Refers to how long you are to continue taking the drug. Sleeping pills are for short-term use and therefore should only be of short duration. This is insomnia which reoccurs when you stop taking the sleeping pill.