Hey there ...

How do you know when you're done with the "weight loss" phase and moving into the "maintenance" phase?

I'm 9 1/2 months out ... 151lbs lost ... and 8 to goal ...

It's really up to you. There is nothing preventing you from losing more weight if you want to. Some people will hit a stall for a while if they are at a set point their body is comfortable with, but just like breaking any stall, increasing activity and shaking up your routine can get things moving again. It's still just mostly basic math of energy in versus energy out. Might just be a little resistance on the part of your body if it's happy where it is.