Well, I think the "16 hour" thing may be an FAA requirement (in order to get
the program approved as a FIRC).

About a year ago, I renewed my CFI using Gleim's on-line program. If you do it
the way it's supposed to be done, then it will probably take you at least 16
hours. Each of the 16 modules in Gleim's program consists of a 20-question
"pre-test" (which is required but does not count toward your grade), a lesson
outline (15 - 25 pages), and a 10-question quiz.

Overall, I though the Gleim program was pretty good. The lesson outlines are in
Adobe Acrobat and can easily be printed out for study or review. After I
completed the program, I printed out my graduation certificate and renewed
through the local FSDO. Gleim can also do the renewal directly (I think this
costs an extra $29 or so).

E. Roberts, CFI