Credit Card Start/Expiry dates

At one time if a card expired in month N, the replacement card would
arrive during month N with a start date of month N+1. The last couple of
replacement cards I have received have been received in month N-1 and
with a start date of month N-1 (eg if the existing card expires 05/08,
the replacement arrives in April with a start date of 04/08). Is this
practice not a little dangerous?
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