Radagast the Brown

[Elessar's Socks]

Riding Like the Wind works the same way. I guess the use of "while" could be misleading, since it might be expected to turn off, but it's a convenient way to govern when the bonus actually triggers. As soon as you can spot 2 mounts, the move limit is +1. Discarding it with Sleep, Caradhras won't affect the modification.

[ephen]

Doesn't seem to make sense but I guess the +1 on move limit is different than the +1 on a card like a promise for some reason thanks to Decipher.

[Elessar's Socks]

Think of it as an exception. This is from the "move limit" entry in the Comprehensive Rulebook:

If the move limit is modified for a turn, then that modification is in effect for the whole turn, even if the conditions for the modification change.

So normally it works like you think. If A Promise is discarded the strength bonus is lost. Move limits just happen to be a special case.

[Gil-Estel]

this indeed looks promising