if you dim your bulbs, your going to replace more often due to lack of efficie cy and your spectrum will be all fucked off.
Dimming your bulbs won't limit life. Actually, the opposite. Anyone that makes this claim clearly doesn't understand electronics. All bulbs, including LED and HID are undervolted from the factory, to INCREASE life. Using super lumens does slightly shorten the life of the bulbs
You will lose a
tiny bit of efficiency when dimming a 1k, but barely noticeable. Same with spectrum. Unless you have a graph showing the spectral shift when dimming a 1k bulb to 750, neither you or the plants will even notice the difference.
One of the most well known lighting companies in the world,
Gavita, makes dimmable ballasts for the professional horticulture industry where even a tiny 2-3% can make the difference. You lose more than that by having glass on your reflector and air cooling your bulbs, so you definitely won't notice a difference in 2000w grow room.
Sure you'll still grow some dank, but do a side by side of a crop Thats been grown via dimmed lights and then a crop where you use different watted lamps and you'll see the differance.
I've done a side by side with clones of the same strain. There is absolutely no difference in yield or quality as long as they have enough light and you don't fuck up something else in your environment/nutrient schedule.