As expensive as flagship phones are they should be grateful anybody ever upgrades.
Considering that most flagship phones blow right past the $1000 mark, I think it's a bit disingenuous for anyone to complain about people wanting to keep their phones as long as possible.
Apart from marginally better cameras each generation, there is no real reason for many not to simply use their phone for 4 or more years.
Then if the phone's batteries happen to magically die after 2 years, most likely anybody not locked into apple will pick a different brand.
Going to a "phone store" to get the phone or a service plan is probably the worst idea ever.
Call up the customer support line on most major carriers here in the USA and they will tell you pretty plainly NOT to go to (their own) branded stores for a phone unless you enjoy being a chump.