It depends... Like initialization(map loading) <- its better to use just one event on the map
Than think if any trigger have any conditions(lets say you have 3 triggers with same event, but one of them takes condition)
But for better preview i would say its better to separate the triggers(lets say every 5 seconds time event...you create units and items, you can put everything in one trigger, but better preview you make 2, because if you need something to fix, you just browse trough triggers and ahhaaa you see here i crate items, and there units...get the point?)