Bob after much research on iphone problems, one that seems to come up is the data port pins in the phone not always getting good connection with USB cable on the or the cable it's self on the data end, any contamination in either can cause problems. These phones are made of micro parts and very sensitive to allot of the elements. It's kind of like a pot switch only it's open to dust and contamination.
They have replacement batteries out that are supposed to have a longer life than original batteries but that is what they say or advertise. I can not say for sure on that. But I think they have a bit higher mAh which I guess in theory would give it a longer run time, not so sure of longer life though. I can say this though, I bought a digital camera 7 years back and at the same time ordered a generic back up battery. The original that came with the camera Died about a year ago would not hold charge it was 1500 mAh the generic battery is rated at 2000 mAh and is still going. Apple is in the business of sales not shelf life.
Next time when you connect the data cable to your computer if the computer is not seeing the phone try slightly wiggling the USB cable on the data end or slide it in and out. See if that helps.