Since I understand Bitcoin better than I did before, my opinion has always been and will remain that every Bitcoiner had motivation that prompted them to invest in Bitcoin, and every Bitcoin investor also has a goal that they have set for their Bitcoin investment. That goal of investment is what can help a bitcoiner decide if they must sell their coin or not; it's the goal that will help them determine when to sell and when not to sell (perhaps a wise and patient investor only wants to sell when they have made a satisfying profit).
There is no one who makes an investment without having any plans or goals in regard to that investment. Some people are investing in Bitcoin just so that their children can inherit it, while others are still holding unto their Bitcoin because they are so rich, and even if they sell their coin, they don't know what to do with the money at the moment. So, it all depends.
You made a very good point, individuals selling their Bitcoin is a personal decision, as you said, every investor has a reason for investing in whatever they chose to invest in and I think without satisfying their curiosity withdrawing or selling some fraction or the whole asset as the case may be won't be an option for them.
It is only an investor without direction that make quick decision about selling their Bitcoin whenever there is drop in price, what makes us good investor is the plan we had before involving ourselves in any investment.
If am to respond to the question of the op, I will say that never sell your Bitcoin isn't a smart advice because no matter how long we decide to hold in the future, we must surely sell one day even though we keep it as inheritance for our children as you said our children may decide to sell it when they finally gain control over the asset, Bitcoin is a profitable investment and the purpose for any investment is to make money, individiduals decide to sell some amount in the future when the investment has matured and reinvest some since the future benefit is assured.