I haven't run the battery down yet - think it reckons 8 hours with GPS on, 30 days with it off.
Re: Garmin 305, yes you can get bargains on older models, but I would be put off by the size of it - I'm going on holiday soon and I'm planning to just take the Soleus and use it as a wrist watch. I also wanted to go take a look at what I was buying. I've only seen those kind of offers on Amazon.