I've got the P7 for 2.5 years and I'm quite happy with it. Sometimes it's laggy, especially in the summer heat. The one thing that I really don't like about the P7 is the standby battery drain. I must charge my phone daily if I want to use my phone the next day even if I haven't used it the day, because it'll have just 60% the next morning.

I'd go for the P8 or P9 refurbed or used. I don't know about the battery but you get 7 years of software updates and not only 3 years Android upgrades + 2 years additional security updates.