Will replacing iPhone 7 Plus battery improve long-term

Not sure what you mean by the battery improving in the long term. If your battery health is below 80%, it will need replaced and the improvement you see in daily usage time will be immediate. Also when the battery has been degraded, performance of the iPhone will be reduced to prevent unwanted shutdowns, so the battery replacement will solve that problem along with lag caused by the battery degradation.

Make sure it is only replaced by Apple or Authorized Apple Service Provider. If you don't have that option you are taking a gamble and nobody knows what you could expect.

Ahmed_812MS wrote:

I love my iPhone 7 plus ( black colour) very much so I have battery issues ( battery health very low ) if I replaced the battery …Does the battery improve in the long term or not? If not, what is the appropriate solution ?

thank you

If you can get Apple to replace the battery in an iPhone 7, it will be a new battery. But keep in mind iPhone 7 is now considered Obsolete by Apple, meaning they may not even stock batteries for them. I understand you like your phone, but putting any money into a phone released in 2016, over 9 years ago isn't a good investment.

You can see if Apple will consider replacing the battery here --> iPhone Battery Replacement - Apple Support

Replacing the battery will improve the runtime of the phone if that's what your asking.