I don’t know specifically about beach glass, but my guess is
that it would take closer to a week (24/7) to tumble beach
glass. I tumble rocks, and it’s a three-part step of which the
first is tumbling them with steel shot and water 24 hours a day
for a week. Then there’s a week more of tumbling with less
abrasive medium, and then another four days with polishing
compound, for a total of 18 days.
Recently, someone in Ganoksin noted a book on tumbling, within
the past couple of weeks. If you check the archives you can get
the name of it and receive more specific on what
media you should use and for what length of time.
-Madeline @ Arts Umbrella