Carbon bike for commuting - concerns about durability
TL;DNR - All else equal, an aluminum framed bike at the same price as a carbon bike will be a better bike. 

My general feeling for Carbon frames are they are overrated, or more accurately, quality modern aluminum frames is underrated. Aluminum frames cost alot less to build than the cheapest carbon, let alone a quality carbon frame. With Hydro forming, the designer has a lot (not all) of the design flexibly of carbon, and a lot more than the days they build frames from tubes.  Savings building the frame can be spent on components, making a better bike at the same price point.  Obviously at the "Money is not issue" end of the market, carbon makes a better frame for riding, but care must be taken because at this end fo teh market carbon layup is done in a way to maximize performance weight, with less concern to robustness. 

As far as robustness and longevity, a quality, but not race focused, carbon frame will be more than robust enough. 

Using the N rule, you really should have two bikes, which will probably be more cost effective longer term. One for commuting which is cheapish (its only 5 miles, a few hundred grams weight saving won't make any difference to you commute times or effort even if it is a bit hilly) and robust. Then have a weened bike for longer rides that you keep the miles down. After a year, the weekend bike is still in great condition rather than having been used in all weather and banged around in the work bike racks by other riders.