I have my Bold-9000 set to auto-off from 5am-530am....i do random battery pulls and when pulls are necessary....just found out about the soft pull (alt+right caps+delete).....
i personally recommend a daily battery pull (scheduled soft reset at 3 am)
Not always needed. Trim the fat off the OS and you won't need to do BP's or use Quickpull. I'm at 504995 secs and counting. And I only pulled it because of a new theme install.
I use the Auto On/Off feature and I don't worry about it. It helps me because I get calls and emails from the east coast and europe so it doesn't stop.
As far as the battery, from what I understand about LiOn batteries is they have a certain number of charge cycles for life span. I don't think all LiOn's are the same but they should be right around 200 charge cycles. I am not a hardware expert but thats what I got from the studying I have done.
I think the average is about 400 times for a LIon battery as I recall.
Also never fully deplete the battery unless it is for a short time.
A LIon battery will not last long when fully discharged. Also, never let the voltage go below 3V or it can be damaged. I have not taken a volt meter to my BB battery yet though when it is below 40% so I am not sure how much power there is at that point.
Anyhow, LIon batteries do not last long, they have a shelf life of about 1 - 1.5 years before you need to throw them out. So never buy extras unless you really need them because they don't last long.
I recommend using QuickPull daily. It has a schedule feature -- I have mine set to run at 1:00 am nightly, just like queuing up back ups and other maintenance for your PC or Mac. My Bold is on 24/7. I don't think it hurts anything for it to be on all the time.