This question is being asked many times on this forum. You can check the answers and most of them will suggest you to save/hold/reinvest your bitcoins for longer times. Now as you stated that you kept 13 cents and it became 50 cents after 7 months or so. Well that change you may find very little but with bigger investments you get bigger returns. Also, you must invest with right time, such as bitcoin price at lower side, this means you will get more bitcoins in less amount spent. Also, when the price increases the same amount of bitcoin will have more dollar value. Thats very easy calculation but basis of how you invest. Household really hold it.