What should my response time be to a ‘bad texter’?

I’m genuinely unsure. i’m not trying to play games or anything, but when someone leaves you unopened for days before responding, what is the correct amount of time you should respond. Usually i really don’t care and would respond within an hour. however this keeps happening and i’ve raised the issue too them but nothing changes.

are you supposed to leave the on read for days as well, or continue responding as you usually do? Or should i just not talk to me people like this🤣
Updates
5 mo
just a bit more information- i have known this person for many years, we’ve very close and when we spend physical time together, there is never an issue, it genuinely is just on the phone. But he’s a guy in his early 20s and his phone never leaves his hand?
What should my response time be to a ‘bad texter’?
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