I finally managed to hook up with a respec TF and tested AB on Test with perma Hasten. 1 recharge does NOT make it perma. 3 recharge does not make it perma. 4 recharge using fresh +3 SOs gives a 5 secs gap. So AB is like hasten, 4 to near perma with Fresh SOs, 5 for those Painful levels. Fresh being levels 37, 42, 47, 49. Painful levels would be 36, 41, 46.
Since I'm 37 I'll respec to 5 hasten, 4 AB and finish 6/5 by 41

Rinse and repeat at 42. Its only 2 slots but that's 2 more slots elsewhere.