Right, sorry for the delay in replying but I have been off work the last week to do my ensuite!
The other weekend I took apart the front brakes on my IS200 and my dads GS300 to replace the pins/boots etc.
All went well, surprised to see that none of the pistons on my dads car were stuck or that the pins were that stiff - all looked well greased still.
With mine, although I had knackered dust boots on my car, from the last time I freed it all (around 2 months ago), all was still looking well. The rubber bush on the bottom pin on the near side was completely gone so god knows where that went!
Anyway, both cars now have new pins etc on the fronts and all seems well.
One thing I also decided on looking at was the rears on mine - and thank go I did. I think the pistons are ok, but the pins/pads were rusty as hell. Had to take caliper off completely and hammer the pads out as the pads was corroded into the caliper housing.
Also means that the inner side mainly of the disk is rusty and pitted so I guess I will have to do them at some point.
So what I would also advise is that people strip and clean the rears as well as the fronts. The pin that keeps the pads in was mega rusty on mine. Also had to clean up and de-rust the caliper where the pads seat and also the pad backings themselves - mainly on the edges.
Little use and lack of maintenance probably caused this!