I've only had this a couple of weeks, so early days regarding battery life. I had a Vileda before this, and to be frank, I preferred that for its cleaning ability: this is quite basic and only good for dust whereas the Vileda had two brushes the breadth of the vacuum and it scooped up loads. However, the Vileda battery started waning after a few months so that it was unable to lift a thing eventually, and I got this for one very specific reason: it boasts about its battery's longevity AND you can get a replacement battery. So, all on all, I'd recommend for a relatively cheap and basic tool.
I've had this a few weeks and very happy so far, it is my first 'Robo Vac' and now I just wish I had got one earlier. I have a cordless Dyson that was very expensive and bought this to just do 'maintenance' cleaning of main, open areas and expected to still do the corners/edges etc with the Dyson. It was quite easy to set up in a few steps attaching the brushes and battery with very easy to follow instructions though the screws seemed as though they wouldn't go in, if you have this problem just keep pushing them in the holes! I love popping this on fully charged when I go out, I shut the doors so it will do half the flat at once (I have a 1 bedroom but is quite large) and it gets into every single corner! If you watch it to start with it looks like it is going over the same patches and moves quite randomly but when left half hour or more really will cover everything thoroughly. The instructions show a little map of how it is programmed to move and this makes more sense. All my flat is hard surfaces so I can't comment on carpet use but it has been brilliant for keeping the place looking much fresher used a couple of times per week and I really do see the difference when I come home and see where it has been left to do its thing. Great value for the price and easy to charge (though does take a long time to be fully changed, haven't times it but at least 3 hrs).