If I have a lot of bitcoin, I think it's best to save it. It's price is still increasing as years go by. Just imagine if you've kept or forgot that you have 10 btc when it first started and sold it today. You would be really rich by not. So, I think if it's not necessary you should just keep it as long as you can.
That doesn't add up at all. You forgot that you have 10BTC and that should mean that you also forgot where is the private key or the wallet seed. You don't even forget about the money that you have underneath your bed, let alone the money that is saved on your computer that you regularly use. But okay, let's say that you actually have 10BTC and you remember (somehow) where are the private keys and somehow the paper that you wrote the private key on is still there safe and sound. You are still not going to be rich. Even in a third world country. Maybe that's a lot of money, but that's not enough to call yourself rich. Rich people have stable businesses and know that they aren't going to go bankrupt for the rest of their lives.