[ehnto]

Have you decided upon a minimum entropy level for the low digit tokens that prevents brute force attacks being feasible? I think easy to type in is something you can do with longer tokens, so long as it's readable as a sentence. "1676226" is harder to type in than "TotallyAgreeableCatPants" for example.

[stavros]

I basically calculated "active tokens at any time", "acceptable probability of collision" and "keyspace bits" and decided on length based on that.

Wordlists are a good solution too, as you say.