Purchasing an iMac in the next few weeks. Is it worth the extra £40 for the wireless keyboard and mouse? I mean...I won't really be using the USB ports on the iMac itself at all. The only thing I would need a port for would be a flash drive, and I can just deal with the 1.1 on the keyboard. When I get a printer I will probably go for a Wi-Fi one anyway. Also, how long is the battery life on the Mouse & Keyboard?