Ilikewood said:
What is a protection pad? How long does pads last? Should i buy two straight away to have a backup?
The protection pads are essentially an intermediate disc that goes between the main pad of the sander and the sandpaper. They are very thin, and have "hooks" on one side and "Loops" on the other. The point is to save wear on the hooks of your main pad. This is really only necessary with mesh (or net) type discs though.
The protection pad is also and adapter of sorts. The hooks on a Festool pad are not the same as the more generic "Velcro". The are smaller/finer and really intended for Festool branded abrasives. They will stick to other brands of sandpaper, but it is not ideal.
Pad life is generally dependent upon how the tool is used. Harder/ longer sessions create some heat, this degrades the foam in the pad. However, time is also a factor. Just sitting, doing nothing has an effect too. Storage conditions may add to this as well.
I have heard people say that 5 years or so can be enough for one to fail, but that has not been my experience. Both of mine are nearing 6 years, with no noticeable damage. I don't use the RO90 every day, but it gets a pretty good workout, in the times I do need it.
All of that said, a back-up is certainly a good idea, but multiples may not be advisable. There is also the hardness of the pad to consider. (at least for the RO, I don't know about the others) There are optional (accessory) pads that are harder and softer, than the one that comes with the tool (when new)
Some people never change them, but I regularly use the hard pad on both of my ROs (90 and 125) and sometimes the soft.
So, I consider the standard pad to be a back-up of sorts. It may not be exactly the same, but it would keep me going.