Stonehenge

What would you say if I asked you how much time you would allow to go 100 miles where you live?

Depends on if you're walking, bussing, bicycling, driving. Depends on the time of day and day of the week.

Can you tell us a little more about your touring style (do you read every sign, listen to every last second of the audio recording, etc)

What about your mobility? (It is possible to walk the kilometer or so from the Visitor's Center to the henge, or you can take a bus).

How are you getting there? (Driving yourself or taking a tour?)

When are you going? (Not only time of year but time of day. Tourist season? I mean, yeah, it's Stonehenge, but even that place ebbs and flows. Also, closer to the middle of the day, more large bus tours arrive)

If you buy your tickets ahead of time it will save you time once you arrive since you won't have to wait in the ticket line.
There is a small museum near the car park. There are two separate exhibits and a movie that can be viewed. Reserve at least 45 minutes to an hour for all of this depending on how thoroughly you want to know the background and history of the stones and the area.
From there you'll ride a shuttle bus to the stones...about a 10 minute ride. You can also walk but that takes longer of course.
Once you are at the stones you can either just look at them, walking the path that loops you around, or you can do the audio tour that describes the stones and their history. That takes about 40 minutes or so.
At minimum I would reserve 2 - 3 hours for the whole visit. You should go as early as possible in the morning to avoid the crowds later on. Tour buses start rolling in about 10 - 10:30 based on my experience.

My wife and I went straight to Stonehenge after arriving at Heathrow at ~9:30am in 2012. This was before the recent remodel wth visitor center. IMHO a half-day would be sufficient, and would allow time to explore the visitor center. If we go back, I'd like to make reservations to walk among the stones either before or after normal hours.

thanks-the United Kingdom guidebook by Steve is recommending a loop starting in Avebury, but that puts you later into Stonehenge which sounds like it would make the place more crowded with tour busses. thanks