Might be an easier way, but you can use $replace...
Code:
$replace($duration(_____),wks,$chr(32) $+ weeks $+ $chr(44),days,$chr(32) $+ days $+ $chr(44),hrs,$chr(32) $+ hours $+ $chr(44),mins,$chr(32) $+ minutes and,secs,$chr(32) $+ seconds)


Just stick your $duration information into there.

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