Vegging for 24 hours under 400W MH

Ok, I read in another thread that vegging under continuous light is bad and you should run 20/4. Last run I did 18/6 and it was satisfactory performance. This time I thought I'd go all out since I got my temps under control now and run the MH for 24/0. The temp still goes from a low of 70F to a high of about 82F. Should I be giving them 4 hours of darkness? It's been almost 1 week since I switched them from 18/6 under a 4 bulb T-5 6500k lamp to the 400 watt MH in the grow tent.

I ran mine 24/0 right after they broke soil from seed all the way to 12/12 flower and I never had a single issue. I use a 400W also.

I'm going to switch it to a 600w hps when I start flowering.

ive ran them all, 18/6, 20/4, 24/0.. etc

i prefer 18/6, less energy usage, and not really a decrease in growth from what ive seen.
my yield has stayed the same as well (actually an increase, but attribute that to learning my plants needs)

I run a 600, 24/7 and have had great results. Plenty of healthy roots in the buckets after harvest. Some folks swear by it some don't. Personal preference I guess.