Only if you feel like it, its not really a race. If it was then I would have pulled up with "cramp" by now as I couldn't keep pace with others here :)
I was thinking about this a while ago, when I read Els' blog post about "Completing Europe," and was considering the impossibility of making much of a dent in that continent's list (someday). I do have some plans in the works, maybe in a year, or a few... :-)
I'm very envious of your first African site being Ambohimanga, it feels suitably obscure.
I relish my life in obscurity. ;-) In fact, just after I made the above post, I took a look at the list of the Most Visited WHS here, and was a little surprised to see that I have only visited 13 of the top 100!