I agree with Richard above. I have used it from a half filled, way past expiry date Kodak bottle when it is as dark as really strong tea, and it has performed like new.
There is a certain amount of water in the air above the fluid in a bottle of HC110. Some of it will be absorbed. I expect that once that water has been absorbed, no further amount will be, unless you add more water to that air. Repeated handling might result in that, but it isn't immediately clear whether there is any net improvement when you compare the handling involved in decanting vs. the handling involved when not decanting.
It is clear to me, though, that you waste more developer when you decant, because it is difficult to impossible to get all of the syrup out of each bottle.
It seems to me that HC110 either reaches an equilibrium with the water in the air above it when you leave it in a bottle, or only deteriorates due to that water at a very, very, very slow rate. I'm not sure that is the case for developers that oxidize due to contact with air.