So many delegates promotion, but how can i still cant choose because there are still questions on my mind on how to do DPOS. Maybe can you enlighten me.
This a simple article that explained what is a DPOS is :
https://themerkle.com/what-is-delegated-proof-of-stake/You can check this list of delegates :
https://lisk.cryptopools.com that offering high rewards on their respective voters
Once I vote, can i shutdown my computer and disconnect from my wallet?
Yes but you must have a access in your Lisk wallet.
How long will my vote be valid?
Once you done in voting some delegate and got a confirmation( with a fee of 1 Lisk )it will became valid.
Do i need to vote again after a week or month?
Nope but you can unvote a delegate.