Remember, If you need help with Helix, it's no longer free. (See /support/index.html) But the good news is that each RADE or Engine purchase or upgrade you make gets you 2 USUs (User Service Units) and each Server purchase or upgrade gets you 4.
If you don't need help but think you might, it can never hurt to have some USUs (User Service Units) "in the bank." Use what you need now, save the rest for later. Volume discounts are available through the web store. (Click the ‘Product’ link at left, then ‘My Account’ to go to the store.) Just login and click the "Buy New Products..." button. The store automatically applies the proper discounts.