I know that these are mainly for reef tanks, but I was wondering whether adding one to my larger tanks would soften the transition from lights off to darkness.

Or can I just put a lamp with a Faint bulb on a timer and have it run all night so there's dim light in my office for all my tanks?

I have a hanging lamp in the center of my fishroom timed on from 10 am till 5 pm when another timer turns the tank lights on.
The lamp comes on again at 11 pm when the tank lights go off, and runs till 12 mid.
This simulates morning and night, the fish don't need bright light all the time, and it saves me a lot of money on hydro with 25 tanks running.

I have 3 timers running 3 type of lighting.

Blue Actinic Lights - ON at 12:00pm - OFF 12:00am

Marine White Lights - ON at 1:00pm - OFF 11:00pm

Blue LED (Moon Effect) - ON at 11:50pm - OFF 6:00am then i get natural light coming into the house.

Geelite and Fever, something along the lines of what you guys are doing is what I'm planning.

Right now I only put the tank lights on manually in the room where I have my two largest tanks. I have a desk lamp with a 60W flourescent bulb that goes on from 5 PM to 2 AM to extend daylight to the evening so the fish aren't asleep when I come to my den. If I do come down then I turn on the tank lights so I get to see everybody.