Yes, those temps are pretty good. Maybe a better CPU cooler would make your CPU last a bit longer, but maybe it's not worth spending 80$ just for that.
Yes, those temps are solid. I've seen a 920 run at 82C under full load for a week and still be fine. (though I wouldn't recommend that)
Sounds like you already have an excellent cooling setup, stick with it.
Also, I don't know how old your i7-920 is but there are a few out there that are 4 years old, that's nothing to be sniffed at.
Yea its a little high but it won't burn your cpu anytime soon. But if you run this 24/7 for a long time, it will shorten the lifespan of the cpu a little. Nothing to worry about, by then the cpu would be obsolete.
Thanks for all the information guys. And good luck to you all.