Most Twitter accounts are suspended for up to 48 hours.
However it depends on the reason of the Twitter account suspension as some Twitter Accounts may be suspended for longer than 48 hours and may last up to a week or more.
For example if you're being spammy, tweet something in violation of the terms and conditions etc then the twitter account may be suspended for a month or longer.
But for simple twitter suspensions the twitter account suspension should be over within 48 hours.
Now when you get a permanently banned from twitter then the twitter ban is for life.
All you can do then is just create a new twitter account and start over.