Skype doesn't do that to me. Only the combination of the Twitter and Skype plugins seriously affect battery life for me such that I'd be in danger of the phone lasting less than a day with my normal usage. It will usually run about 30 hours if I don't use it a lot, 16 to 24 if I use it more. Much less if I watch a bunch of videos, obviously.

I'm always logged in to Ovi, Skype, and two SIP accounts.

This is on WiFi and EDGE.