Laptops are a bit different, mainly because they tend to be a bit warm inside, and in the office they tend to stay on the mains power at all times.. the combination of temperature and 100% charge isn't good for lithium batteries, they like to be a bit cooler or to keep the charge a bit lower (they can handle temperature a bit better then). All laptops here at work are quickly reduced to 10-15 minutes battery lifetime because they are 24/7 on mains.. after I replaced the battery in mine I now use it off mains a lot of the time and the capacity is still good after a year.

I used to charge my T3 PDA over night every night, and sometimes mid-day too, and after two years the battery capacity was still good. But it's a lot cooler, which seems to make a big difference, combined with the different usage pattern (charge, use battery a bit, charge..)