I think $5.11 in your first 12 days is good going.
I have over 40 Hubs and been a Hubber for about two years and you are making slightly more than me a day.
Most of my earnings come from 6 Hubs. So they fit in with Pareto's 80/20 principle - 70-80% of your earnings will come from 20-30% of your Hubs.
So at your current rate, you should be making about $155 a year from those 12 hubs, and will hopefully do so every year, even if you never write another Hub.
An interesting way to look at your Hub earnings is to work out how much money you would need to have in a bank account, paying 5% interest a year, to earn the same £155 a year?
You would probably need about $3100 in your bank account.
How long did it take to write your Hubs? How long would it take you in a job to earn $3100?
For me that is why I would rather spend an hour writing a hub, than an hour at work. I get more "interest" on the time spent.
Good Luck with your future hubs.