He must have better access to the space time continuum than everyone else then - I tend to put manic tweeters into a low attention span, high hand waving for attention group who only have a few hours left in their day to actually do anything else...
What he probably has access to is people who review his feed and replies and curate that for him. So he's not responding to tweets he's found himself; but rather to tweets that have been highlighted for him to respond to (if he so desires). Heck, his team might actually include possible response ideas.
The fallacy is thinking Elon uses Twitter like any other person uses Twitter. Sitting on his device, manually scrolling through it and replying sequentially. He's probably outsourced much of this to his media teams or other people he trusts to provide relevant material to engage with.
Not a time waste. Look at Elon. He spends a lot of his time in engaging at Twitter