User interviews usually last from 30 mins to an hour. Sometimes, when you need to dive deep into details, it can take up to 1.5 hours — but these cases are rare exceptions. Generally, people lose attention during longer interviews. This means that the quality of information you'll get will decline.

Aim for 30-45 mins per session. This will give you enough time to break the ice at the beginning and wrap up at the end. It's also short enough so that interviews don't feel like an unmanageable time commitment for you or the participant.

Try to wrap up the interview on time, showing users that you respect their time. If you run out of time before asking all questions, ask participants if it'd be ok to reach out for a follow-up.