Dr McGill recommends a 6-4-2 holds of 8-10 seconds in his book Back Mechanic. So you do 6x10sec of bird dogs + rest 30 sec, same other side, then 4x10sec + 30 sec rest, same other side, then 2x10sec + rest 30 sec, same other side. Switch to curl-ups 6-4-2 then side planks (L/R) 6-4-2. I took about 3-5 sec rest in between holds just to set myself up properly each time.
I found 6-4-2 to be too long to do frequently and it ate up too much of my training time so I just did 3-2-1 instead and found it to be plenty. Although I aimed to do it everyday like the Dr recommends, 4-5 times seemed to be what I was able to do consistently.
EDIT: 6-4-2 took me almost 20 mins to complete. 3-2-1 10 minutes or less. Keep in mind you can/should apply tension techniques when doing the Big3.