There is no investment in bitcoin that is risk free the fact that long term investment is prioritise over short term investment doesn't mean that so long as one is investing in long term is a guarantee of success.bitcoin is best appreciated when view in terms of long term because short term investment involves high risk due to the volatile nature of bitcoin and also there is always greater potential of loss .
Of course bitcoin investment is risky but among all the investments one can think of bitcoin is less riskier than others when we compare it to stock and/or bounds. It's also true that nothing is guaranteed but then looking at bitcoin from the past history and events around it you will find it convincing to know that bitcoin is more guaranteed over any other type of investment.
Investing in bitcoin for short term is simply put calling bitcoin a bubble and/or Ponzi scheme/ get rich quick scheme however bitcoin is beyond that, I call it a swan and/or paradigm as it is the first of its kind, the technology that shifted the thoughts of people for basically the fiat standard to a digital money.