As a long term investor,if you do see that you are profiting with a certain coin, would you let it pass? For sure you will consider on selling it up.
I think there's also a thing about proving it as a currency (to yourself).
I might spend a small fraction of the btc I hold (10% maximum maybe) just to check that it still works to buy physical goods and is still accepted (as I anticipate it to be)...
I plan on putting what I plan to spend in the future into bitcoin and see if it increases by the time I spend it (find a point when the coin is low and dollar cost average out of it instead), but I'd have to be pretty certain of my stance.