I will offer you a little info gleaned from several years in the distributor business. The average life rating on a T12 Rapid Start Lamp operated on a rapid start circuit will be @18000 hours, while it would be @15000 hours on a preheat circuit. High efficiency T8 Lamps rating would be @15000 hours when operated on an instant start ballast, and @20000 hours when operated on a rapid start ballast. Although the newer 8' T8 lamps can only be operated on instant start circuits. To obtain the best life in 8' fixtures you would need to use the ones that require four 4' lamps. Along with the higher cost the high efficiency T8's are 40% more efficient when used with the electronic ballasts. They are also essentially flicker free which makes working under them much easier. One other often overlooked advantage to the electronic ballasts which is especially economical on large installations is the large amounts of heat produced by magnetic ballast is not produced by the electronics. This factor alone can more than offset the higher initial cost in a lower air conditioning load that can be factored into the job, both in a lower quantity installed and less power to operate. The average life rating is based on 3 hours per start operation. The lamp life hour ratings may differ from one manufacturer to another, but the percentages are probably close as far as how they relate to the circuit the lamp is operated on. The T8's and electronic ballasts cost more because they are worth it. The different circuits mentioned are the ballast options that are available. Did I leave anything out, or can go ahead and write this order up now?