Old Iphones & Old people

I have an old Iphone 4 and I've realized that it ages pretty much in the same way that human beings do.

•  It now seems very bulky, especially when it lies next to its younger relatives; 
• the picture quality has significantly deteriorated, similar to old folks losing their sight; 
• the battery has become very weak and needs to be charged several times a day, kind of like an old person with low stamina; 
• It's also become very slow at doing everything; the memory gets filled up frequently and it needs to delete new memories to make space for newer ones; 
• the body is a bit worn out; it's very difficult to find stylish cases, heck, it's hard to find any case for it. Nobody makes stylish clothes for old people. I wonder why though.

For these reasons, I think I may need a new phone, but I want one with a longer life span than an Iphone. Three years is simply not long enough for a phone to start exhibiting signs of a seventy year old man! What shall I do? Leave it as is and try to squeeze another 3 years out of it or upgrade and experience old age again in 2-3 years time?