You can use the Hps all the way through really........... I've done so with great success.......and lots of people here on this site also.......I prefer fluorescent tubes for my veg room personally....... HID creates to much heat and requires extra equipment to cool down.....but for flowering hps is a must for me........CFLs work great (for vegging) I just hate all those wires all over the place. 4 tube Fluorescent fixture ......one wire .......and a easy 12,000 lumen output.I got 6 tubes with an estimated output of 18,000 lumens in my veg room