I've been booking tickets almost a year in advance to get a good price and often the flights are changed and rebooked by LH. If they give me a bad connection (eg 6h in frankfurt) then I call them and they rebook something better, but often the new booking class is different even though I don't have to pay anything for the rebooking.
And the miles are credited as per the new booking class (although it's normally the 750 miles class, but at least it's better than the 125miles i would get otherwise).