If you click on the "What are Troth Tokens?" link right between where your troth tokens and your donuts are, then it has a little explanation.
If we go by that, then you reach 10 tokens on the 29th consecutive day.
So, just about a month.
Now, personally? In practice? It takes me about four months to get there, because I keep resetting my streak. >.<;
Edit: 29th day from starting from the very first time.
It's a week between each boost upwards; so once you're on 8, then just six more days and you can look forward to 10
