Today when users are connected to their system for endless hours, on the internet in the past this wasn't the case.
On bulletin board systems users had a certain time frame they could use while online, it may have been a hour possibly more depending on the system and if it was a pay system or not.
Many bulletin board systems used a deposit and withdrawal system like your local bank, users could be allowed to make time deposits and withdrawals up to a maximum amount based on the systems operators configurations.This allowed the user the ability on certain calls into the bulletin board system to have more time online or store time for a later use.
Many bulletin board systems where so active they didn't use this option, meaning the user had a one shot deal for the day it could have been two logins or maybe a certain amount of time online allowed.
Many however used a feature called a Time Bank that allowed the user to store and withdraw time for use on a later call into the bbs.
Some bulletin board systems this was a built in feature on other's this was a door application...