Most of the LCDs with backlight are having 2 LED pins and they consume
100mA at 4.4Volts. Consider this with power consumption of LCD module which is just about 1mA !!!
I think one should apply switching circuit to energise the LEDs and
save the power. For example if we drive the -LED terminal with the BC639
and some 10 ohm resistor to limit the current to 100mA then with 10% duty
cycle the LCD backlight will be same as driven by direct +5V. Only disadvantage will be another ckt to produce this driving or use spare HPWM
signal. I hope then the +5V regulators would run "cool".
I have used circuit like this for LED displays and they appear so bright
as directly driven.