yea i would just put em in the same room even.... one six hundred watt lamp on 12/12 will cost you 20$ a month to run; assuming that your paying 7-8 cents a kilowatt hour. so thats only like 50$ a month including your fans and shit like that. i run about 1200 watts right now in our house and our electric bill rarely gets over 70. thats nothing.
when i was living with two buddies of mine last year two of us were very conservative with energy and electricity. the other guy stayed in his room all day and night, running a space heater, a computer hooked up to a 48" moniter, a fan, dvd player, vcr, stereo system and like 3 lights TWENTY FOUR SEVEN. he was a cokehead so yes the lights were on all night. our electric bill was always $200+ every month solely because of this guy. did the electric company come knocking on our door accompanied by the police? nope. because you have to remember that the electric companies are NATURAL MONOPOLIES. they are there to make money because this is capitalism. they aren't going to knock on your door and say "hey! you're using too much of our product! you're giving us too much money!" Do you think that the electric companies in california are complaining post prop 215? that being said, that doesnt mean you shouldn't be cautious. i wouldn't do anything like put 10k of lighting in a single bedroom, as thats probable cause and who wants to find out if they call the cops or not haha