What's the max amount of time a transaction can stay unconfirmed ?
There is no maximum imposed by the Bitcoin protocol, but since the computers on which it runs are made of matter, the laws of physics impose an upper bound on the length of time they can exist. Your transactions will certainly cease to exist within 10
40 years when all atomic particles break down, unless the universe (or at least the Bitcoin network) is destroyed some other way before then.
Two of my transactions are still unconfirmed after 48-72 hours and it seems like they will never confirm. However, i read they will eventually be rejected or something and return.
You read wrong. Most software will continue to broadcast your transactions until they are confirmed with no easy way to stop it.
Already fucked as i needed the BTC two days ago, but just wondering how long will it still take...
What fee (if any) was paid on these transactions? If no fees were paid, you may be waiting a while longer. Use the time to complain about the software or service used to create the transactions, since it is clearly defective.