Bitcoin is a long-term investment therefore holding beyond 5 years is even more preferable, we've seen how it's risen in the past decade so you can imagine how it would be like in the next decade, there're even hope that the price could be up to $1m by then so I think those who only invest for a full circle should consider extending their long-term plan to a decade or more, the beauty of holding Bitcoin is that no amount is too small so far the holder is considering holding for a very long period, you can do it daily, weekly or monthly and according to the income you generate. The more you hold Bitcoin, the more advantage you get compared to someone who's held for a lesser period someone who's held Bitcoin for a decade or 2 decades would be at more advantage and profit compared to someone who held for 5 years due to the ability of the coin increasing over time.
Many people have proven and felt that when they hold it for a long time, they can eventually get big profits,
Holding Bitcoin for long term is a very good way to go with Bitcoin investment however big profit like you said is not still guaranteed because no one is really sure of the future at come of Bitcoin, yes with the way Bitcoin is going right now for example more people getting to know about Bitcoin and investing in it and nations and states now having a Bitcoin reserve, with this there's a great hope for Bitcoin in the future but there can also be a change of things in the future which may not be in the future of Bitcoin so therefore even those investing on Bitcoin for a long term are also taking risk because there profit or gains are not 100 percent guaranteed.
Some newbies who are into Bitcoin investment where told that as long as they buy and hold Bitcoin for long term they can eventually get big profits and they decided to join without knowing that even with the long term holding is still risky.
It will be more better that when telling someone to start Bitcoin investment and you tell them about what they stand to gain you also tell them the risk involved.