There's probably no "right" answer. It does take about 5-6 weeks for milk supply to be established, so definitely you did the right thing by pumping constantly up until now. At this point, you can probably safely play around with your schedule and see what happens. Power pumping is a great idea; it helps mimic a nursing baby's normal rhythm and can help you fit in those extra minutes of pumping. Just be sure that all your long pumping sessions aren't replaced by quickie sessions. As far as nighttime puming, you're getting up to feed your baby, right? That's a good time to pump. No need to set an alarm. You might also want to use power pumping strategies for nighttime - keep a cooler beside your bed w/ all your pump equipment, pump, then stick the whole flange setup into the cooler. As long as your DD is healthy and has no immune system issues, it's usually safe to reuse the same flange more than once. NIghttime feedings or pumpings really help to keep your hormone levels (and therefore milk production) high.
You might want to read about pumping and supply at www.lowmilksupply.org, and/or the book by the same author (Diana West, IBCLC) "Breastfeeding Mother's Guide to Making More Milk." There are lots of ideas about scheduling pumping and power pumping.
Oh, forgot to mention storage capacity. That's the maximum amount your breasts can hold between feedings and is only partially related to breast size (women with small breasts are more likely to have a smaller storage capacity, but larger breasts doesn't necessarily mean larger capacity). If you have a small capacity, you'll have to continue pumping frequently to meet your DD's needs. Women w/ a larger capacity are more likely to be able to space out pumping (or feeding) sessions more. You probably already have a general idea of your storage capacity - when you go longer between sessions, do you get a lot more milk? Women w/ large capacities may be able to pump 10 oz or more at one sitting, those of us w/ smaller capacities may be happy to get 4 oz. You'll also feel "full" more rapidly w/ a smaller capacity. Frequently waiting until you feel "full" to pump can lower overall supply, as full breasts are a signal to your body to slow milk production.
Yes, I was going to say this. If you do notice any drop, at this point it's unlikely to make any permanent difference as long as you're able and willing to pump a bit extra over the next couple of days to bring it back up.
I haven't been on much lately but I did see your responses & wanted to say thank you for your advice! I have been able to space out pumping without noticing a drop in supply. It's comforting to know that I'll be able to recover from a drop with extra pumping if it ever happens. The hardest part about maintaining my supply has been trying not to stress out over it.
It seems I have a small storage capacity. The max I've pumped (after a long sleep during which DH fed DD) was 5oz but it's usually only 2 oz. every 2 hours.