.... altitude this climb gradient must be maintained (normally, it says something like ''maintain it until 4000' or so). So, until which altitude do l have to fly with this? For the whole SID (until RIDAR) or what?

http://i213.photobucket.com/albums/cc115/PilotFerdi/az.jpg

Since no altitude is specified, l would contend that the climb gradient is required until reaching FL70, since that is the cleared altitude on the SID.

FL70. This climb gradient is based on an airspace constraint so the gradient is needed all the way up to the depicted altitude.

l agree with the 7,000 that the other two have said. If it does not specify, then l would assume it is required up to whatever the initial climb clearance altitude is.