I think you have to look at the game as a whole. I'll be willing to bet that the vast majority of the in game population (not just forums) do not have 17 toons zeta and are wondering how they can get more. You said yourself (op) that "they are a "big decision" and should be used as such..." and so that is the answer.
You have 17 zetas and feel the game has slighted you because the zetas run their course over time. Well, I would say the majority of toons and therefore all of their abilities run their course in the game as well. Should you get a buy back gear program for maxed jawas, droids, night sisters, Greedo. Should you get all of those credits back and shards? Sounds silly. No offense, but no difference with zetas.
You seem to be able to collect zetas at a higher than average rate, so just keep doing the same, or make some slightly harder choices about when to zeta like most people do. I don't think the devs meant for anyone to have all of the zetas and keep up with all of the new ones at all times. May seem surprising, but that'd be my bet.