Yes I use the wall charger. But I just made sure to use a 500 mAH charger in hopes the battery will last longer including longevity and longer battery life. As Spkrs mentioned it can take a very long time from full drain and I don't intend on leaving my PC on all day or night to just charge a DAP lol. So I use my mini surge protector which has usb charge ports on it rated at 500 mAH. So it works perfectly to PC USB specs. I'll generally charge while sleeping. From now on I'll charge it when its on 1 or 2 bars.
I think what spkrs and Lee said has reassured me this is normal behaviour. Now I can rest I'm not over charging the battery.