Once per year seems rather hard on the 5th and 4th and sometimes even 3rd kyus... Some of them could easily have got their day requirements several times over in one year.
We are supposed to have like 90 hours (since attaining 5th kyu) or so for 4th kyu and I have over 200 (tested in November for 5th kyu). Truthfully, it doesn't bother me at all that testing is held once a year or less. Either way you are still learning the same thing as everyone else. Rank means little to me.... I think people get too wrapped up in testing and gaining rank sometimes.