Can I use an old Smoothing Pad for anything?

Absolutely!

One of the best tools in our shop is an old smoothing pad.

When you get a new smoothing pad, you're most likely still going to be using your existing electroplated disks. The new smoothing pad will be much more aggressive than you've probably now gotten used to and will create a bit of an annoyance when you realize that your polish time is now increasing again.

Simple fix, go from the new smoothing pad, to the old smoothing pad, then to your polish and you'll find that your polish time will diminish dramatically.

See, even old things have their uses.