This is a very complicated question and one that I just don’t think we have an answer to yet. My best guess for knowing when you are ready to keep an anemone is best represented by this quote from
@Eagle_Steve (aka Grandpa Anemone Master).
“This is where you are going to get that your tank is too new. While this is partially true, if you have the time and dedication to keep things stable, not make a 1000 changes all at once, a BTA can be kept.
If you do not have that ability or the tank swings all over the place, in terms of parameters and the light is not sufficient, it will lead to the death of the nem”
This may or may not be applicable to condys and tube anemones but I think in general it is better advice than “you just need to wait 6 months to a year”. Especially because there is so much we don’t know about keeping these animals in captivity and what makes them happy vs. what makes them sick. When I started a thread asking what a mature tank was, I liked someone’s answer that went something like “sometimes the general guidelines for 6mo-1yr are just to give the reefer time to do enough research, get to know their tank, and know how to respond to changes in your tank” I’m not sure there is any special sauce that is magically produced at 1 year and I definitely think you can be successful with anemones much sooner as long as you are dedicated to do the research and do things using current best practices.
sorry for the long response but I hope this helps!