usa – How to renew a US visa for a Dubai expat?

I’m an Egyptian working in Dubai, UAE as an expat. I had a B1/B2 Us visa that expired 2 weeks ago. I travelled twice before to the US to attend technical conferences.
My US visa was originally issue 5 years ago in Cairo, Egypt.

Where should I apply for renewing the visa? Egypt or UAE?
I have no plans to travel to the US in the near future. Can I still renew the visa? or do I have to have a valid travel reason to renew it?
Is it a problem if I don’t renew the visa right now and wait for a couple of years in the future for example?