Ive noticed that during winter I only need to wate...

99% or so of the water the plants drink is later transpired. Because of your low temperatures, the plant is transpiring very little and so, its needs of water are greatly reduced. It is not a matter of UFO vs HID vs whatever; if you can raise your temperatures, then your plants will start drinking more water, the ideal situation is to water for 4 to 5 days. For your temperatures 1.25 liters a week is too much; I would give it half a liter and expect it to last 3 or 4 days. Having the soil wet too long can (and usually will) attract bugs. If you can raise your temperatures, you will see an increase in growth (or bud development) speed; try to lower your exhaust fan speed or have it on a timer (15 in on / 15 min off).