It depends on how do you define long. If 1 year is long enough for you than do not invest but if 10 years or more you are talking about than I think you should invest
Holding too long can also be risky if price drops in future, if you see higher price then you should sell it in order to make quick profits as you can buy again when price falls.
in order to not lose any target profits i simply use stop loss orders. it means that if the price goes down while i didn't expect the drop, that i don't lose my profits. i'm an intense user of that feature as i don't like seeing my profits decreasing when the price suddenly starts dropping. it gives you as trader good confidence.