Attach the skirting board immediately after tiling or later

Always install baseboards immediately. Depending on the insulation used and the readiness of the covering (some put the coverings on too early), you will hardly have any cracks at the maintenance joints. And if you do, just repair them as Saruss says – in many places it is difficult to access later and after the construction phase you want to finally have it nice somewhere, right?

Well - it was not after 2 years, but at the end of the heating period - so in April/May (move-in February).

Makes even less sense

I don't even want to think about how many pieces of furniture, etc. would have to be moved, shifted, and emptied so that this can be done afterwards. Not to mention places that are hard to reach for the joint (under the toilet, sink + wall-mounted washbasin, for example)...

I don’t even want to think about how many pieces of furniture, etc., would have to be moved, shifted, and emptied so that this could be done afterwards.

Yes, that’s just how it is! With cracked joints, you also have to move the furniture again, but then you have additional costs and the manual labor involved. Our screed, although well dried, apparently sank by half a centimeter. Not only are the joints cracked, but it also held in other places, while the baseboard tiles have detached. But fortunately, that falls under the warranty...

Would you like to write how you repaired it? As far as I know, silicone does not adhere to silicone.

The silicone sticks to silicone for me. I sprayed it from the can onto the crack after wiping it once with a cloth. Then I went over it once with a plastic scraper, wet it, smoothed it with my finger, done. As I said, out of over 70m of baseboard/seam, 30cm is cracked. All baseboard tiles are absolutely fine.