I think holding the bitcoin for a long time is good although its depending on what you of course consider as a long time.
Most of the times a long time can be good its just a matter of time these days to make profit with the bitcoin.
yeah, for how long you will hold your bitcoin, but I think if you are into long term keeping, you could try it for one year first, if there is an improvement in price then keep it for 2 and add few more in your stash then if it works, well, that's the time you have to decide if you are going to sell it and keep it for another year. But you have a point there that nowadays, the price could really tempt you to sell it and regret if you are on the wrong timing.
I think we need to be specific on how long we should hold our bitcoins, let us say if we are planning to hold it for 10 years then the better as long as we will monitor the price movement and we have a target also when to sell for a profit or for a lose.