Is it worth it to transition into more open lines when one is used to closed, positional games? I've played the French and Queen's Gambit, which tend to lead to more closed, positional play.  I've played these openings consistently for roughly 25+ years now, with no set opening before then really.  I did try to learn both the Center counter, or Scandinavian, and the Danish early but eventually gave up and played random moves (I was quite young).  After that it was Petrov for a year, then on to closed games.  I'm currently 38 and have been at closed positions now for 25+ years.  By consistent I mean every single game I've played since then.  If it is relevant my USCF is around 1500, with a peak of 1620.
From a strong expert:

Just because I find open games to be more fun, I would suggest playing more open games.  Also a variety of openings will expand your knowledge.  (Looking at your tournament history, you may already have enough knowledge.)  Just like you don't quit smoking in one day, don't switch to overly aggressive opening.  Try the Scotch, Vienna, or Giuoco Piano.  These openings requires the learning of more opening traps, but they should improve your quality of play.

Assuming that you have the time to invest in studying an opening, learn the common positions and plans.  If after trying this style you feel uncomfortable, go back to playing the closed/positional games.  If the game is not fun, it is not worth playing.

When I reached expert level, I switched to a more positional game because I thought this is what was supposed to happen.  I lost many games because I hid my talent.  

Some GM said that he switched to d4 because he got lazy as he got old.  Anna Zatonskih said that with d4, White can make more mistakes before losing the game.  You could be hanging on to the safety of known avenues.