To create a memorized timesheet, you have to go into the Memorized Sheets page and create a new timesheet from scratch, then save it. Most people probably don't think about using a memorized timesheet until they have repeatedly edited and saved a tedious timesheet. Then they go to Memorized Sheets and have to create it all over again, just to save it.
How about adding a link or button on the Time Sheet Entry pages to simply save your current timesheet as a memorized sheet?
Travis Bauscher