Please interpret

The announcer was reading from a chart-------"Remember to change the batteries in your carbon monoxide detector after no more than 5 years."  I have trouble enough parsing out double negatives, but find this even more incoherent.  When does after the no more than 5 years period kick in?  IN no more than 5 years may seem comprehensible. Would substituting "before" for "after''  clarify the timeline? Confound it!