I would try doing the 16 mile ride. That's a pretty long commute and you might find that you don't want to commute that far. If you are going to commute by bike once a week, then that bike won't be too bad. But if you think you'll be commuting by bike 3+ days per week, you might find you'll want a different bike. How many hills are then and what is your average speed? If you do find you like commuting, then you'll probably want to replace the bike. For a commute that long, I would recommend a bike with drop bars which has more aerodynamic ride. And you have to consider how much faster you might be on a better bike. I have an 8.7 mile commute, but there are a number of stops for red lights so moving time != wall clock time even at 16 mph. I would not rush out and buy a bike right away until you have some experience on the existing bike.