When to use just bloom switch on led Bestva 1500 using both veg

use only veg light for 2-3 weeks max. when the plant is grown andhealthy u can switch bloom as well.

Leaving both on the entire grow is fine, those switches are more of a power saver, I used to use a light like that, and I always ran it with both switches on for the entire grow. Happy growing.

I wouldn't use it till your last week if you do. I believe with those types of lights the power is cut in half when only using the VEG or BLOOM by themselves. It is suggested to use both during flower so your light intensity is high. You could get a voltmeter and test the wattage at the outlet when using each and both to make sure. Hope this helps.