milking foot fetish

My sub has a footfetish and once i milked him he doesnt get submissive for a very long time...
I love to tease him with my feet and step on his balls and even kick them but everytime i milked him he gets out of the mood for weeks,is this normal?
I have read that some others have the same problem with their footfetish slave...but no one knew why...
Maybe there is a foot fetish slave out their who can tell me.
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This puzzels me BIG time