road bike setup and commuting

I have a question, I guess it's muscular related...

I am going to start cycling to work starting either Tuesday or Wednesday. I'll be using my road bike. Over the weekend I took off the aerobars so I could fit a light and computer on the bars. I wasn't sure if I should put my old road bike seat post on though, right now I have a Profile Design Fast Forward seat post. My commute is 8.5 miles both ways. The most miles I've biked in one week was 209 miles, so commuting mileage shouldn't be an issue, even if I throw a century in on the weekend (wouldn't want to do that too often though :-]). I was thinking this:

Option A - keep it on, and maintain some type of triathlon muscular strength/endurance over the course of my "off time". Or could I overuse the muscles over time if I do this?

Option B - remove it and put my old road bike seat post back on, and build up different cycling muscles in the leg, maybe not as beneficial to triathlon. Will this "save" my triathlon specific muscles from being overused?

Option C - does it really matter? should I do whatever is more comfy since I'll be doing this as much as possible? I can spin a lot easier when further back on the bike.

I appreciate any input, or other options!