Oh!
One other thing that no one has mentioned!
Maxxing abilities is an important part of the game. Zetas are incredibly important, as I'm sure you know. But many people don't always pay attention to Omega abilities. You're just starting to Omega your characters now. I'd just like to take a moment to tell you that even important characters can have abilities you don't want to spend Omegas on.
Just like zetas, there are better and worse Omega abilties, and even great characters can have abilities that aren't worth the Omega mats for that final push. Fives has an Omega that gives Taunt, for instance, but also has a zeta that sacrifices the toon to get huge bonuses if another character is killed first. The truth is that you probably don't want the taunt once you have the zeta, but you can't get them back once you spend Omegas to improve an ability, so if you later zeta Fives you'll still have an ability that conflicts with the zeta ability AND you'll have lost 5 Omegas on that ability you don't want.
Fives is also just an example; there are plenty of Omega abilities like this. For instance you never want to Omega the Geonosians' Hive Mind abilities unless you have Brood Alpha unlocked and geared up to a useful level. Even then, some of the Hive Mind bonuses (which are all Omega abilities) are either counterproductive (like Fives' taunt) or just not worth it.
With all the talk about zetas, you might think that Omegas are something you won't need to worry about long term, but you will. Don't use them without thinking carefully about which ones give you the best bang for your buck.