If you have 30 flights/day, then yes, some will have to leave close together. But in this case, close together means 30 minutes.
5 minutes separation is too close, and will be penalised.
Scheduling flights very close together was basically a way to rort the system, and so Sami fixed it.
To play it safe, on most routes, you should never have flights leaving with a gap smaller than 1 hour. On very busy routes, like CGH-SDU, you should never have flights leaving closer together than 30 minutes.