I want to set a general song length for multi track tunes. I mean I want to have my loops repeat for a set period of time,appr. 5 min .. so I can keep some structure..I will adjust the final time later if I want. I see how you can drag the loop and have it repeat 25 times or so but then you run out of room on the screen. How can I just set the loops repeat for a specific amount of time. It will help me stay organized.

You can set the Project (song) length by dragging the small triangle at the upper right to the desired length (see screenshot below); selecting a Region and hitting "L" will loop the region to that Project (song) end point—toggle "L" to turn looping on & off for the selected region(s). Of course you can still drag the upper right corner of any region to change/set the loop length individually. I'm not sure what your level of expertise is, so I'm adding a link to a video that discusses using the (normally hidden) Arrange Track, in case that might relate to what you're looking to do..