arduino wifi shield and ip lease

hello. Looking at the arduino official wifi shield library I can't see anything like an equivalent of the ethernet.mantain() function for reneving the ip addres once the lease has expired. This is not dicrectly handled by the shield, if I change ip from my router and I do not execute once again the wifi.begin() it stays with the old ip number. I do not want to call the wifi.begin() every time I need to send packets on the net because this solution is too much stupid. Do you have any suggestion to solve this problem in a more optimized way?
thanks in advance for any suggestion.

Looking at the wifi shield behaviour I think the IP lease is managed directly by the firmware and that it is not necessary to care about as we need to do in the ethernet library.