All of these are dependent.
An elephant gets a peanut as long as she picks up a brush.
'as long as' shows that the elephant gets the peanut if she picks up the brush.
if we change that to 'but', then
An elephant gets a peanut but she picks up a brush
then the 'but' in the sentence makes it seem as if there was a previous condition that showed consequences for picking up the brush.
If we use except there, then
An elephant gets a peanut except she picks up a brush
it shows much the same as 'but', as if there was a condition previously stated.
An elephant gets a peanut barring she picks up a brush
'barring' shows that she only gets the peanut if she picks up the brush, much like 'as long as'.
To simplify, 'as long as' and 'barring' have the same meaning, to get something, be it praise, an object or something else entirely if the subject completes an action.
'But' and 'except' both mean that the situation is still conditional, and is usually used in a negative context, as if the subject has already done whatever it is that is not supposed to be done, or they have defied the conditions completely and done something else entirely.
I hope this helped.
