How fast can you count cards?

I performed my fastest count to date at 18 sec tonight, but I'm not consistent at this time yet, probably at 60-70%. But its late and my eyes are tired, I'll try again tomorrow and see if I do better when I'm rested.

I'm well aware being able to master 35-40 sec is really all you need. I just want to be able to count fast in the event that I could purposely turn my head away from the table then suddenly look back when all the cards are out and count out the whole table instantly

my speed

i can consistently count down a single deck accurately in about 20 secs with a best of 16 secs however when counting through 8 decks (the number used in my local casino) i can rarely get the right count, i'm usually off by 1 or 2, but sometimes more... does anyone have any methods for keeping track of the count better for longer periods of time as in shoe games?

thanks

nightfoxx