I know it’s an estimate.
In my experience, the tip doesn’t turn yellow as the pod nears the end of its development, but rather the color put on subtle brownish hue for darker pods and slightly yellow brown for green.
Most had no color changes.
I'd guess that if it splits before 9 months you aren't going to get anything - it is a dud. If you can wait 9-10 months you are probably very safe to do it green.
Fair warning, that type of breeding can be extremely difficult to bloom. Not sure about the germination rates, but I wouldn't expect many seedlings. I have some roth x maudiae types that I've had for 25+ years that still haven't bloomed. Why? I'm more stubborn than smart. I don't have many and every year I compost a few. Doesn't mean you shouldn't try, there have to be some combinations that work. But I'd advise bailing out before the 25 year mark.
All this may change with new rothschildianum breeding. I'm told we are at 4th or 5th generation from the wild at this point. These new ones germinate prolifically and grow much much faster than anything that was around even 10 years ago. So maybe those roth x maudiae crosses will bloom faster too.