i have one question..
in 2011 bitcoins per 50,000 to 500,000 we spent for nothing, just pranking and stuff...
if one person kept 50,000 bitcoins in his account from 2011 up till now,
would the bitcoins still be valid for transactions?
Yes, i do not think bitcoin has validity period. So, if he can still access to his wallet then he can sell his coins or for whatsoever purpose it will be. But if he cannot access to his wallet, then his bitcoin will just sleep in there.
Yeah, the only thing that can make that invalid is when such a person has totally lost the private keys and apparently no access to the wallet again whatsoever, then that is considered lost forever. However, as long as the keys are still intact and the person can still easily access the wallet no matter how long it is kept in it, then there is nothing that is going to be affecting it at all. Obviously, once the person in question has a target to sell them when he is ready, he definitely will.
Bitcoin old and new will have the same value, so far I know bitcoin does not have "Expiry Period" during circulation is still ongoing and can be used as a tool of transactions both for trading and investment.
As long as it is still bitcoin and nothing changed whatsoever which I believe nothing will, there is nothing that is going to end up invalid for transaction for bitcoin. The only reason why it could no longer be used for transaction is if there is no more access to such wallet and the person obviously cannot do any transaction in such scenario, except for that, it is always going to be valid for transaction.