If I understand your OP, you have a Voyage already, correct? If so, I'd suggest keeping that and waiting to see if Amazon comes out with something better in the fall. It doesn't hurt to have a second ereader device, or you can always re-sell your Voyage later--they remain popular. Personally having tried one, I think the Oasis is a nice device but is not going to give you a night-vs-day improved reading experience over your Voyage. In fact, it may not be better at all. I actually like my new 32GB PW4 *much* better than the Oasis 2 I just tried. And as you've guessed, while the battery life is not bad and not less than Amazon promises in their ads, it *is* most definitely lower than that of your Voyage, as well as some other popular devices I've tried recently such as Kobo Clara, Kobo Forma, and PW4. It's perfectly adequate if you set your expectations accordingly, but it's also true you can do better, and you already have better.

If it were me, I'd enjoy using your Voyage, hang onto it and keep reading, and see if Amazon comes out with something that is really a nice step up this fall. Heck that's only 6 months away. And if you aren't impressed with their new offering by then, there'll probably be a plethora of other choices, including new e-ink devices, new Android e-ink tablets, new Android tablets, etc.