Advice??

I know there are some teachers out there... any advice as to how to write your Leave letter?  At this point I plan on returning to work, but I am trying to write it as "tentative" as possible so that they don't hold me to a specific date of when I am leaving or coming back.  (My district allows 8 weeks paid leave and up to 15 months unpaid leave.)  I just don't want to write myself into a corner!  :)