Don't respond to every message posted. If you are compelled to send this type of message, send it to the original sender only and not to the whole listserv. Keep your e-mail address current. Listservs vary greatly in the amount of traffic generated. It is a good idea to begin with one list at a time to gouge the time involvement.
Some lists generate hundreds of messages a week, others only a few.
It may be helpful to determine if your lists allow you to put your mail on hold while you are on vacation, or you may be overwhelmed on your return to your e-mail. Read and delete your messages regularly. It may be helpful to create a mailbox or folder in your e-mail program to hold those messages that you would like to save. You should certainly save the instructions for unsubscribing to that particular listserv. Some people find it helpful to create a mailbox or folder for all of their listserv instructions.