My phone actually lasts the whole day now thanks to a battery change.
I got my 7+ on launch day, and had my battery changed yesterday. It was at 88%. They did not update my phone.
I used to charge on average 2 times a day with the iPad charger to get through the day. I got through today with—currently at 40% of heavy usage, browsing, social media, YouTube.
Totally worth it.
I recommend changing your battery before Dec 31 !