One of the things to keep an eye on is that not all power sources will give the max current available through one USB port. I was reading about the one you tweeted the other day, and there were a couple users that said that they had issues where the port flagged for apple should be used for the iPhone and the port for Android stuff should be used on that one.
There can be some negotiating with the power supplies in some of the smarter supplies with smartphones, however, PlasmaTrim simply wants to draw what it needs as it needs it.
Unfortunately on that gorilla, it doesn't list the actual max current for 5v, which is the USB voltage. This will ultimately be the limiting factor on how many units can be on full white at any given time. The mAh rating is what will tell you how long it will last. It is possible that the specs they provided meant to say 1000ma, which is 1 Amp, same as our 2-port AC adapters.
Thinking about it from full white, each PlasmaTrim will draw 0.5 Amps, or 500 mA. 2 of them would be 1A, 4 would be 2A, etc. 10 PlasmaTrims would require 5 Amps. I don't know how likely you are to find a supply that will provide 5 amps out of one or two USB ports to then go through hubs, but you may find hubs that will take additional power and could run off of the 12volt output.
Without getting lost in the details, assuming it could handle 5000mA consumption and a storage of 21,000mAh, that's just over 4 hours of run time at full power, which is also a worst case, since you may be more likely to do something more festively colored, maybe even not needing the full brightness.
Everybody impressed with NASA thinking about all this for conservation of energy for the rovers on Mars? ...same basic thing, the more you use, the faster the batteries drain, and they can only be replenished so fast with the solar panels. Use more than you can recharge, and say good bye to the rover.
Outlets on Mars... That will be the day!
"Those who say it can't be done should get out of the way of those who are doing it."