The scheduling options for recurring events in our current version (9.0.2) is limited to essentially to 5 very limiting options.
1) Once a year a particular date
2) Once a month on a particular date
3) Once a day at a particular hour/minute
4) Once an hour at a particular minute
5) Once a minute
Only the first 3 are usable to any real extent. We have many process frequencies that cannot be supported by these options without building additional processes around them or intentionally allowing the processes to fail.
Adding more sophisticated recurrence options would make the scheduler tool a much more useful function and decrease the amount of effort required to work around it's limitations. A good example of the recurrence options that would be useful can be found in Outlook for meeting recurrences.