I'm still managing with old splinter guards. This past year I adjusted all of my splinter guards (eight I think, and all black) out so they correctly indicate the saw cut. Some of them are from 2003 and they still stick good enough for me.
I warm up the guide rail and rubber strip with a heat gun then gently peel up a few inches and more it out a mm or so and stick it back down. I peel it up just enough to make a hump in the rubber strip so I can easily get a grip on the next section and lift some more. Don't stretch it too much and let it shrink back before pressing into place. Working this way also minimizes contamination and oxidation which will degrade the adhesive.
As everything cools down it becomes harder to lift the rubber off the adhesive without tearing the adhesive. The adhesive when warm releases from the rubber easier than from the aluminum and if it starts coming off the aluminum with the rubber you'll end up with a double layer in spots when the rubber is put back down. So, when it becomes difficult to lift the rubber cleanly from the adhesive you have to warm everything up again.
When the whole strip has been moved out to the new position I heat everything up again to reactivate the adhesive then clamp a straight strip of wood (about as wide and thick as the rubber strip and also at least as long) with a lot of closely spaced spring clamps. I leave them on as long as it takes to get the next rail up to be point of needing the clamps.
Clamp the ends of the strip especially well and often. The residual stretch in the rubber will affect the ends most and they'll loosen. So clamp them again later. Also, there is more air intrusion at the ends so the adhesive is less active. However, just because the ends of the rubber strip get a little loose doesn't mean the rest of the strip is unreliable. The ends rarely even matter. The saw blade can't reach there unless the rail is joined to another and you don't use that uncut section for registration either. So, if the end looseness bothers you there is no harm in adding another layer of fresh adhesive there, but only there.
If you replace the adhesive keep in mind that Festool uses a very thin matrix of paper. Get something that is also thin, no thicker than 3M double stick tape. I wouldn't use anything that doesn't have a consistent mechanically controlled thickness. That is, don't use something that has to be spread or sprayed. Thick tape will throw off the effective bevel of the saw (slightly) but you don't want to have one rail that requires you to adjust the saw bevel.
