Well...I just do a track selection.. between 10 and 14
I like to let the songs play their beautiful sounds.. so i don't rush mixing them as fast as possible... I usually start the mix at the last minute of the track (for 128 beats) this is the average...
some times I do a quicker mix (last 64 beats) or ,sometimes the songs I play have smooth and long build ups... and long ending... so I do near a 2 minutes mix (256 beats or 192 beats)
anyways... I just play my records till I pass 70 min of mixing... then I prepare a last mix... if I have time for a last song I play it.
the result should get near 80 min..
If its too much... I pitch up the entire mix in a wave editor so it can fit in a 80 min CD.