-F option

manual page states that

       -F     Disable an automatic fsync()  call  after  each  transaction.   This  option
              improves  performance,  but an operating system crash while a transaction is
              in progress may cause the loss of the most recently  entered  data.  Without
              the  fsync()  call the data is buffered by the operating system, and written
              to disk sometime later.

What I would like to know is what 'sometime later' means.
Is it one hour? 30 seconds? 30 minutes?  24 hours?  I really don't
mind losing the last 3 minutes or so of data.  If we are talking about 10
hours or so then I will not use that switch.  I'm not looking
for an answer with milisecond accuracy; just an upper bound +- 5 minutes
will be ok.

My usage is frequent lookup of small pieces of information, ocassionally
insert of small pieces of information and even less frequent update of small pieces
of information.  I have 7.0.3 on linux 2.2.18 and accessing from Apache::DBI
mod_perl.  I have about three tables or so with the largest table being over 1000 rows
and growing. Is postgres an overkill for this size of data?

Thanks