Facebook Ads Suspention

I have advertised the wrong things on facebook Admittly,
I have emailed them explaining i wont do the same again and that it was a mistake ( as i skipped t&c's)

How long do it usually take for them to unblock accounts ?

Depends what you did wrong. If you advertised diet, skin, muscle or similar affiliate offers, forget about getting your account back. Usually fb sends you an email saying something like 'This decision is final' and 'you should not under any circumstances advertise again'.

If you did something that is against their TOS, or your ad got reported or an admin of the page related to your niche reported you.. You will receive an email within 24 hours that your account is permanently banned. But if you receive something like unusual activity and you just get flagged for it. They will send a reply after 4 days. It will also depend on your explanation and what you have submitted.

You probably won't get it back if the account isn't aged
The reply to the email can take a while, ive been waiting for 10 days now

If the email sent from fb contains such thing that you are permanently blocked, then it means their decision is final and can't be reversed. But if they says the block is temporary, in that case follow their instructions properly and your account should be reinstate.