Actually I disagree on previous comment. Singularity can auto-duplicate them, became vampire (dealing damage to you when they attack), play chaos power on themselves, adrenaline, etc. A vampire+adrenaline singularity deals to you a lot of damage and can kill you before your dragons start to attack. You shouldn't use two SN in a row unless you're planning to win in this or next round. Don't make a singularity at the start, definitely.
But still I think there is no big difference, you still need at least 6-7 rounds in order to play the combo, so there isn't a particular reason to play 2 SN in the same round in a normal situation. If the situation requires it, just play according to it (you can even play 3-4 SN in a row and play chimera if you don't need it after, since they are gonna be killed and save you a little damage from enemy creatures).