I work alone with the computer for extended periods of time. I also compulsively waste time searching the internet for useless or naughty tidbits. Most of the useful work is done offline. Tried a modem control program, but it would not lock out the administrator. I must be the administrator to do the work.
Locked the modem in a box with an appliance timer. Gave the combination to a couple of friends from http://www.sexaa.org/meetings.htm, who can stop by if changes to timing routine are required. (I don't know the combination.) A to-do list helps to manage the limited online time I now have. It works!