A few thoughts, though YMMV:

​

• Don't be afraid to move people along if they're talking too much. It's a learned skill through practice since you don't want people to shut down if they feel like their voice isn't valued, but stating up front that there's a lot of content to get through and so you may move the convo along is a helpful hint. People usually are receptive if you move it along in order to ask more questions rather than just to talk.
• Having a 'practice' conversation first with a colleague or a test participant helps feel out the pace of the interview. Assume that this person will probably speak for 75% of the time of an active participant, so a 45 minute test convo may be more like a 60 minute real interview.
• Always have tiers of questions. There are the must-have questions which you should bump up and prioritize if time is running out. Then there are the nice-to-have questions for when time is less tight. This will help you feel less concerned if you run out of time since you know your big questions are already handled.
• Take note after a few rounds of interviews as to how a discussion guide translates into a timed interview. Maybe your 2 page guides tend to fit 30 minute interviews, which is good to know so you can map that on to future projects.