Let me guess: you've previously used Pro Tools, or some other click/measure-guided software before taking up Audition. Join the club!
When starting with Adobe Audition, one of the most important things to learn is how the edit track mode and the multitrack mode work together. When recording voiceovers, edit track is usually the preferred recording view. If you're recording a song with instruments, multitrack view is usually used. Either way, both views allow you to send a clip from one view to the other: edit to multitrack by right clicking and selecting "send to multitrack", or multi to edit view by double clicking an audio clip in multitrack view. Many multitrack recording programs expect you to do all of your editing solely in the multitrack and mixing views. In Audition you can edit in both these familiar multi and mixer modes as well- but the edit track view is an important addition unique to Audition.
Most of the people I know who use Audition have a common goal in their workflow: output a single, final-product audio file, completely edited, mixed, and mastered... and it all happens inside the single program without sending the file anywhere or to anyone to complete the process. (This is why I personally use Audition.) To complete a project from creation to mastering, edit track view becomes extremely important.
I think you're on this step. Once all multitrack editing and mixing is complete, the workflow moves into mastering. when you've finished with editing, mixing, and effects in the multitrack view, mix down the multitrack audio clips into a file this way: lasso-select the desired session clips, right click inside the selected area and choose "mix down selection to new file". (There are other ways to do this, but this is the way I most commonly use.) The machine will show a progress bar as a mixdown is being created. (This is usually very fast, system pending- but with clips an hour long it might take a minute or two...) Once it's complete it automatically switches to edit track view to show you your complete mixdown. You'll see a single audio file, displayed as a mono/stereo/multichannel waveform. This is the finished product from your multitrack session, and it's ready for mastering with Audition's built-in mastering racks and dynamics processing. You'll notice that this track will be the exact length of your 1 hour clips. After mastering, save the file in whatever format you need, and there's your finished product. (If needed, this is when you would go to CD view to prepare audio to be burned to disc.)
As you can see, edit track view is the place where sessions are sent to draw them to completion. This changes the typical role of a multitrack editor a little bit- it becomes more like a workspace and less like the final canvas. There's a freedom of what things are laid out on the multitrack when you have the ability to select what you want to send to the final mix without having to move or change the multitrack clips. This is the perspective I think you're missing when you say you want to reduce your session duration. Honestly, I'm not sure if it's possible or not to change a default session duration, but as you get used to the zooming and scrolling methods I doubt you'd even notice the extra space. (After 5yrs experience with Audition/CEP professionally, I had no idea there was an 8 hour session duration.)
I bet your worry is that by having an 8 hour multitrack session, you predict that you'll end up with 8 hours of audio when you're ready to export. This is not the case- the only audio mixed down is the audio selected, OR the audio within the session if you choose to mix down all clips in session instead of selecting files to mix down (make sure you don't have any rogue clips way out on the timeline). As a miniscule downside of your session not ending spot on with the end, you have to hit the space bar to end playback at the end of the clips; but if I were going to do any reverb, delay, speed changes, or other effects with trails or time adjustments, I definitely would appreciate having that extra room at the end of the clips to work with. The extra space at the end also makes for a good "work space" area for setting aside clips not in use in the rest of the multitrack session.
If you have any more questions, feel free to ask. It helps to clarify what kind of project you're working on, what software version you're using, and anything else that might help tailor an answer to your specific needs.
Good luck! Everyone here was a beginner at some point, and everyone has something they still can learn.
Actually, my most similar experience has been with Final Cut Pro, which has a similar (though less elaborate) track approach. It allows me to control the overall duration of the project, which is useful (if for nothing else) to keep the display consistent with the scale of the project.
However, I just noticed that clicking the "zoom out full" button reduced the duration of the session to just a little more than my longest track. That works fine for me. So I guess I just answered my own question.