I have some XT brakes on my bike and they are about 3 or 4 years old.
As you would expect they have slowly got worse over time with the levers needing to be pulled further and further back to achieve the same stopping power.
So they got to the point where they were both touching the bars and I decided I could no longer put it off - I would have to sort them out, which I understood to mean changing the oil and removing any air from the system.
I've now done that and they are much better, but definitely no-where near as good as they were when I got them. They now engage much more firmly and at a much earlier point in the lever stroke, but after that I can still pull the lever back quite a lot more, which I guess you would describe as a "sponey" feel. I'm sure they were not like that when they were new.
Yes I have done the oil change and bleed properly. In fact I have done it properly twice just to be sure. I have the official shimano bleed kit and I followed the instructions, plus read a few alternative instructions online to make sure I wasn't missing anything.
Also the pads are new and so are the discs as I got some new wheels recently so thought I might as well put new discs on them.
So, I have come to the only remaining conclusion which is that there must be something else in the system that is worn out or needs servicing.
All I can think of is:
1) Brake hoses. Do these degrade with use or over time? Could they be contributing to the spongey feel?
2) Seals within the callipers. There must be some sort of seals around the pistons in there - could they be a problem. Are they user serviceable?
So what do you all think?
Any ideas or knowledge you can share on this would be appreciated.