The station with the display on and with a network card draws about 200 mA at 24 Volts, which translates to 5 Watts. This is certainly more than what network devices usually draw, but it is impossible to lit a 7 inch display without power. The display can be dimmed, which reduces the wattage by around 1 W.. A 7 device loop would therefore draw a total of 1.4 A at 24V. When you select the 4-wire cable use a gauge with a Voltage drop of not more than 4 Volts. The data cable pair should be twisted.
The back-lite of the display is rated to at least 50’000 hours at full brightness. The chosen brightness of a non dimmed display is 40 % lower and of a dimmed display 80 % lower. The expected life time of the back light should exceed 10 years.
SIP-SNAP 