Yah. The longer BTC is held, the better the profit would be. The price has increased now and it is going to go more. Many have already seen the profits and again bought more bitcoins and holding it looking for a price more hike. Too much investments now would pile up the wallets with good profits. Almost everyone is waiting for the moments to cherish.
i agree with you and you are right that longer bitcoin holding is very profitable and adoption of bitcoin increasing and bitcoin price is also increasing too much quickly day to day and people buying bitcoin and then hold it for high price and its way is very profitable .
It wont be profitable if you hold it for so long time while in fact you can use it to get more profit by trading instead of just holding it. i.e you hold 10bitcoin now (bought it with rate $640) means you have spent $6,4k then you hold it lets say till the price up to$1000 each but you need to wait around 5years to reach.
Lets calculate it : your profit after 5 years = $260 x 10 = $2600 for 5 years. It is only around $44/month. I think it is not worth enough because with 10btc you may earn more than $44/month by trading.