Is afk farming on something like a mob farm not allowed or does that not work?

I read something in a thread which said going afk for too long can get your server deleted, so is going afk on a farm considered against the rules?

Quote from Alex [ES]

Being afk for too long circumvents the Aternos system, but using farms is allowed, just don't afk.

Maybe I'll just afk farm for like half an hour every now and then

or is that also not allowed?