We have a bunch of rules around auto response campaigns, so take a good look at them.
In general, posting many Tweets with a similar format may result in Botmaker (our anti spam technology) marking your account as spammy / suspending the account requiring phone number verification, so be careful there. Your account may also not show up in the search index.
You’re correct about the posting limits of 2400 Tweets per day. This can sometimes be higher in the cases of verified brand accounts, which may explain why you’re seeing higher numbers on some accounts. It doesn’t sound like you need to exceed this limit anyway if you are expecting 600 entries per day.
In general, I’d repeat that you should read through the Developer Policy and Agreement carefully and the Automation guide I’ve linked above - it is very hard to say whether or not you’ll definitely hit a road bump here; the guidance is to avoid spammy and noisy apps which would be a poor user experience.
