Glad you’re enjoying the effects of <a href="http://www.t-nation.com/store/products/z-12"target=“new”>Z-12!
Since Z-12 is a non-addictive formula (unlike a lot of sleep aids) and it’s main workhorse component, PhGABA, has no known side effects, it’s assumed Z-12 safe to use long-term with no drawbacks. In fact, all three components of Z-12 have healthful effects, so you’re comparison of Z-12 to a daily multi-virtamin or Superfood is pretty accurate.
Furthermore, 5-HTP helps PhGABA and L-theanine to keep on working without allowing you to develop tolerance. So, it keeps working every single time, unlike melatonin.
On a personal note, I once used Z-12 for an entire year at full dosage with no ill effects. (Now I just use it as needed.) So we’d say if you enjoy Z-12 nightly, you’re good to go.
Just heed the warning label of course when it comes to taking it with certain prescription drugs, and don’t take it when you’ve been drinking alcohol.