I see some potential variables here; do you use tick or second charts? They take lots more data than minute charts. And what number of symbols do you watch in streaming real time quotes at a time?
I started using Verizon data card services, and moved to Sprint when Verizon did the 5 GB deal to their unlimited data access customers. Now Sprint has done the same thing. I think all 3 major data card providers, Verizon, Sprint, ATT all unfortunately now have this 5 GB limit.
With satellite you probably are already used to some greater than cable data lag; reliability may be so so depending where you are relative to nearest tower and how busy the area is. My Sprint cards drop off randomly, not too often but they do it. Also, is this just for trading use? You will find if you are data card only, as I often am, that surfing, program updates, internet radio all can help use up your data limit. I have bumped the 5gb limit and throttled myself down, or postponed downloads until the next month to avoid the overage situation. If it's all you can get, it's way better than dial up, but it sure isn't high speed cable.