I can't comment on the point someone else made about the incorrect location of the nail, but WRT the plastic material, you should be OK for several years. Overall, it just may not last as long as a metal one.
I assume your roof is somewhat low pitched on a single story house, which is why you felt comfortable going up on the roof to take pictures. Worse comes to worse, just go back up there after a few years armed with a caulk gun or a new vent.
yea my roof is weird. 50% flat and 50% sloped shingles. i had a huge thread about redoing my roof last year. you can dig it up for pics if you like. i been up there plenty of times now and it's nice and flat on the flat side