Two MH Questions

[JeffDubya]

Question 1:

With my diving equipment, I use compact HID lights. Granted, they are very different from MH lighting, but there are similarities.

With HID, when you turn on the light and fire the ballast, you really NEED to wait a minimum of two minutes before you turn it off. I am told this is to save the bulb.

I notice a similar start up sequence with my MH (14K) pendant, and I am wondering... once that pendant is turned on, should I wait any particular amount of time before shutting it off?

Question 2:

For my prop tank, I am currently using a 12 hour photoperiod. Too long? Just right? Please let me know.