I had the same problem! I haven't gone through 8 pairs of boots though, I had issues like that, I'd have to take my boots off in the morning after riding for an hour cause it hurt pretty bad, then I might have to do it a couple more times through-out the day and I would be good at other times. To stop this, this season i bought superfeet insoles, they worked perfectly! Also play with the lacing on your boots, you said BOA made it worse and it is probably because its easier to tighten your boots and you end up over-tightening them, do your boots up so they are on snug, not loose but they are holding onto your feet snugly-tight, if that means anything. I have burton speedzone boots, 2011 Ambush and I find myself easily over tightening my boots, it has worked for my problems, sometimes I still get it but it is wayyyyy better than last season where it was almost every single day
Note: After reading that switchback thread argument I really don't feel like reading any more, sorry for the inconvenience if anything I stated was mentioned earlier.