When I bounce down (mix) the audio clip is 1 hour long! Why??

Hi.  This is probably a strange problem, but it happens every time I use Sonar. I record a lot of tracks and sometimes some long takes (raw recordings of sound effects etc) and sometimes I'll drag sound clips far to the right (past the 10 minute mark) just to get them out of the way for a while.
 
But when I bounce down to a stereo mix it takes a long time (15-20 minutes) and I end up with a really long song that is mostly silence. The mix I just did is now over 60 minutes long even though I just went though and cleaned out anything that was past the 13 minute mark. 
 
So, is there some way I can limit the bounce process? There doesn't seem to be a time setting on that page. I know I can highlight just the things I want to mix but that's not easy with my songs. I have a lot of tracks (142 in this one) and the songs are often 10 minutes long. 
 
Or, conversely, is there a way I can get it to stop thinking that it needs to keep going well past the last sound/midi clip in the project?
 
Thanks!
Scott

Or after selecting the tracks, click-drag across the timeline. There are several ways to select a time range to export.

I had the same issue, sometimes creating an envelope would put something way beyond anything I'd recorded.  I set the Now Time marker at the end of my song, and when exporting select Edit->Select->Thru=End.  Same effect as entering and end time though.  It works for me as I put an END marker at the end of my song, and it's a quick way to just drop the Now Time marker there.

If you hit Ctrl + End and your Now time marker relocates to somewhere other than the notional end of your project, then there most definitely is something out there that's causing it.
 
First check your event list - select ALL tracks and scroll to the bottom of the screen to find out where the last events are.
If there's nothing there, you need you check envelope nodes, tempo changes, meter/key changes. These last 2 have their own dedicated View screen so open it up and examine the contents of each.