iphone

[car10002]

Hi

What other clues does phone usually provide to tell you it's time to upgrade to the 6 or 7? Have a iphone 4 and it's doing following

batterys lucky to last a few hours even hardly using it
Cameras not working best
Phones very slow and freezes
Signal drops out at certain places and in certain buildings yet the 5 onwards is almost perfect in same spots.

Why would the signal drop out on a 4 when the 5 on is fine in same spots

And why would the 4 freeze up yet the 5 on is quick

Would above problems plus how long you had it tell you it's time

Is there anything you can do to the 4 to run latest and to buy you more time to save up for the 6

How come the older iphones stop working properly after certain time why don't they just have some upgrades to keep them going for oldies so they don't have to keep changing once they're used to it and for people that need their old iphones to hang on a bit longer

What are other clues it's time to update from your old iphone besides slowing down

Thanks for any answers and help