It's often debated if your average signal should hover around -12 db or -20 db, it's a question of how much headroom you want to allow for the peak portion of your program, which should not go over 0 db. It also has lots to do with the overall dynamic range of your mix. As long as you have a good signal with peaks and valleys that average around -12 dB with plenty of peaking up the -3 db range and a few right to 0 db (it's good to use a limiter on the final mix), don't be too concerned about some of the program being closer to -12 db than 0 db, as long as the average hover just over -12db. -20 average makes sense for production recording, but for a final mix you're better off with -12db average and a healthy number of peaks in the -6db to -3db range.

A separate issue is dealing with other formats downstream, one issue is that if you have most of the peaks right up against the 0 dB brick wall all of the time, you might have a problem with distortion if you then go to an analog format downsteam like Betacam SP (assuming you line up -12db reference TONE on your NLE to 0db analog on the analog system). 0db analog still allows for quite a bit of headroom with +3db analog peaks not considered a problem, in fact it is good to see a reasonable number of peaks over 0 dB analog.