Please stop asking the same question with different numbers. 8 nodes, 1,000 nodes, 1 hour, 6 hours, your question has been answered: you simply must make sure the devices do not transmit simultaneously. That’s all we can say. See also How many gateways are needed to support 1,000 nodes sending 10 bytes per 5 minutes? And for those calculations too: take into account that you’re not the only one using the shared radio spectrum, now or in the future.