#1
when shredding:

I heard MAB and some other fast guitarists say that when one does alternate picking it is ALWAYS down up down up...

so a run would look like this

---1--2--3-------------------------
-------------1--2--3----------------
-----------------------1--2--3------

D--U--D--U--D--U-D--U--D

D=DOWN
U=UP

now that works obviously perfectly well, but does it mean it is wrong if some one does this:

---1--2--3-------------------------
-------------1--2--3----------------
-----------------------1--2--3------

U--D--U--U--D--U--U--D---U

I play the second way and it doesnt hurt me or affect me (i think) and it seems to be more economical.

what are your opinions?
#2
I think what they mean is; you don't play "DownDownDownDownDown" or "UpUpUpUpUp", but you have to alternate... updownupdownupdown and downupdownupdownup are pretty much the same I guess

I fell asleep on my arm once, scariest thing that ever happened to me. I thought it was kill.
#3
strict alternate picking is down-up-down-up.

what you are doing is known as economy picking. it's fine. but it's not strictly alternate picking. MAB (and most guitar teachers) would probably suggest you practise both.