CVS has the regular Boost nutritional drink multipack on sale for $5.99 and get a $1 ECB back. Use the $3/1 printable HERE and get the multipack for $1.99.
Boost Nutritional Drink, 6 ct, $5.99
Earn $1 ECB
Use $3/1 printable HERE
Final Cost: $1.99
I did this deal yesterday and my limit has not been reached yet, so it looks like you should be able to do this deal more than once.