An elder showed me Psalm 45:16. He explained to me that the elders would be the princes of that scripture. To be sure, the scripture is there for a reason but I think far too many JW got a notion that Jehovah's kingdom would resemble mankind's systems. A prince would need servants so he can focus on his princely duties. At some point, maybe a few thousand years into paradise I would think we just got back to basics of growing food, making what we need and trading as needed. It's not like we need skyscrapers and Walmarts. Commercial industry would be a concept forgotten but there would be what we need.
Electronics? I won't say not at all but what would we need them for? TV and Radio would be pointless. Is there really anything on TV we can't live without? Instead of radio I would think you just go see a live show or maybe those so inclined get together for a jam session at the latest picnic. A gym would be unneeded because we would be doing real work that would keep us in shape. After 40,000 years I could see someone getting tired of going to the gym.
If you have eternity to live, some things just don't matter any more.