Yes, the ethernet will be on 24/7 or the IC will not be soldered at all to save cost.
I'm trying to get the most out of stm32f4.
At the moment the project is expected to have almost everything, USB device port, USB host port, Ethernet port, RS232, OLED, SD, GPIO, wifi, bluetooth, zigbee, GPIO, etc.
Maybe later I'll write a driver for a USB 3G data modem connected to the host port but at the moment I think I already have too much work to do.
At the moment I guess I'll go for two crystals, on for the MCU and one for the PHY.