There's no exact time limit that a cop can hold you at a traffic stop and detain you.
However if the traffic stop is still going on after 30 minutes you should ask the officer what is going on and try to get it on video on whether the cop says you're free to go or you're being detained.
Most traffic stops should take no longer than 20 to 30 minutes and if it lasts longer than 30 minutes then they may be waiting on backup because they may have found something on you.
Or you might have a warrant that they are verifying before arresting you.
If you do have a warrant they are required to arrest you and bring you into jail for the warrant so if you know you have a warrant and the police have pulled you over then be prepared to get arrested.
If the officer tells you that you're not being detained then you're free to go but get it on video to prove it to the courts if they decide to try to stay they didn't say you're free to go.