I start seedlings in 24 hour light for about 3 weeks but I'm not too sure about the vege state. Fluoro lights do not generate much heat which means you can put them only inches away from the tops of your plants. The amount of lights you need depends all on the number of plants your growing and the space your growing in. I believe the general rule of thumb is 2000 lumens per square foot will work, 2500 is good, and 3000 is optimal. If you only have a few plants, pick up a fixture that holds two 4 foot fluoro bulbs. If you're planning to move them outdoors theres really no need to invest in any lighting more serious than fluoros. My personal opinion would be that if you want to keep a 24 hour light cycle for convenience, invest a few bucks in a timer and you're set.