Well, I have done many smoothies but not as an actual gig in bulk.
However, I read your last post and asked my daughter, who
worked for and managed a Juice-it-Up for 3 years--thats all they DO
is make smoothies.
So she recommends:
1) If possible, 2 blenders per worker--this greatly speeds up the process,
allowing the second blender to be filled, while the first is whirring.
Then serve first one, clean, fill, turn on.....then serve second one, clean, fill and so on.
She says it also depends on ingreds and how many different flavors youre offering,
which you havent told us yet.
2) Frozen fruit is best, theyd get it in 30 lb boxes: pineapple, banana, strawberry and peach
most popular. Reason for frozen over fresh, first is cleanup-- a time comsuming part of the process,
is much easier. Fresh makes a huge mess. Secondly, better cconsistency with frozen.
Third, frozen gives a "head start" on the smoothie freezing process, cutting down on blend time
and on having to "adjust" the mixture--again....consistency.
Also, for maximum speed and consistency, they used, in this order:
crushed ice, juice, fruit, and frozen yogurt (vanilla or plain) (in 5 gallon tubs)
Theyd also use sherbet sometimes, also very popular.
She also says that those commercial blenders hold a LOT, like (4) 16 oz smoothies from 1 blender.
Which is another reason for using a second blender--as the first may not get emptied straight away,
especially if making different flavors.
She added that the most important thing of all is to keep-the-blenders-going.....as constantly
as posssible.
Hope that was helpful--I found it rather informative myself. 
