For whatever this is worth, I never make them. They take time to pay for themselves, so if you start spamming them you actually lose mass for something like 10-12 minutes (the first SCU will pay for itself long before then, but by then you have several more produced that put you into debt more than the first SCU benefits you so it takes longer than the time for the first one to pay for itself for the SCUs + Gateway to start helping your economy).
If someone starts spamming them, they're effectively giving you a 10-12 minute window where you will have more available mass to punish them with. Rather than trying to outeco them during this period, just make a big ass army and crush them.
I play 10x10s though, so this may not make sense on say, Seton's where there is a significant travel time component for your forces.
So, if you want to be able to play like a high rated elite 700 on 1v1, or 1200 in global... you know not to build RAS SCUs =P