It's between you and the bank. Nothing to do with immigration. It's like having a phone on contract: can you keep it after your leave expires? After all, it's just a service.
Some banks may forget about you. Some other, may ask you to update your details from time to time. If they realise you are not in the country, some may offer to switch to a non resident account (mind the fees!!!), some may freeze it, some may close it...
I recommend going to see them and tell them you are leaving the country and what are your options to keep the account.