Jul 7, 2017 - 2:57 PM
There's also a "Sommerabonnement" for the Jungfrau Region for CHF 560. I don't have much details but it could be the best choice for such a long stay as it's valid for the entire summer. You could ask about it at the station in Wengen. Note that it's just for that region, so day trips beyond Interlaken are not included.