From my experience, the reason accounts usually get suspended so fast isn’t just the number of messages but how they’re sent. If you blast 300 identical texts in one go, WhatsApp flags it right away. What works better is slowing the process down, mixing up your message content, and keeping activity closer to how a normal user would chat.
Some tools (for example, WupHub) are built to handle this by letting you schedule messages, rotate templates, and spread them out over time. It doesn’t make you “ban-proof,” but it definitely reduces the chances compared to pure blasting.