Chris,
I moved this over to Gear Care because I think you'll get more eyes on this that will be able to weigh in with thoughts.
That being said, the quick answer to your question is yes.
Depending on who you ask.
There have been articles posted listing the dangers of 'over conditioning' leather and that the conditioner can actually damage the leather fibers over time. There's also be articles posted stating more or less the opposite opinion and the worst thing that will happen is the 'extra' conditioner will just sit on the surface of the leather and need to be buffed off with a clean cotton cloth (old t-shirt is my choice).
We've had members used an entire tub of Pecard on one jacket with no ill effects. Personally, that's overkill to me. The general rule of thumb is to give a jacket a coating before it goes into 'off season' storage and another before wearing the jacket exposing the jacket to the elements during 'jacket season'. The exception to that would be if the jacket gets a really good soaking, it can be advisable to give it a treatment after it completely air dries as the drying process will in itself dry out the leather.
Keep in mind any of the leather conditioners are not dyes (unless it specifically contains dye, some Pecard products do) so the darken effect will be temporary. Basically like a wet shirt will appear darker when it's wet. Once the conditioner soaks in the leather will lighten again per your experience.
Regards,
Indiana Jeff