You should not invest it at all because why should you, with holding it for a long term you can maybe become a rich man.
Because if you invest those coins you can get significant returns and when compounded with the rise in price of bitcoin it will allow you to get even more profit even faster, those that are holding but don't have many coins will have to wait for a massive rise in price.
If you do not have enough experience and knowledge about the investment, just hold your bitcoin. But if you confident with your skill, do not waste your time and see bitcoin price is getting higher and higher.
Yes, holding also means that it value will grow as bitcoin prices always increases.