Hi MSR,
Resetting is a very bad idea since you might get duplicates.
In addition to what Frederic mentioned above, in case you think the number range can get exhausted so quickly try considering a NUMC10 or 12 data elements so that you get close to a billion numbers.
If you still think this is going to run out, in SNRO, on Number range object change screen, set the "To-Year" flag. this lets you configure ranges against a year.
So when you call the NUMBER_GET_NEXT , specify the year(GJAHR) as well.
Don't forget to make GJAHR a part of your table's primary key.
Good luck!
Vimal