This is a tough one to really track down, but here's what I'm seeing:

If a token attribute is used in an e-mail template, sometimes the result is blank, sometimes it prints out an out-of-date value; both when used alone (e.g., {TOKEN:ATTRIBUTE_1} ) and when used as part of a function (e.g., {strtotime(TOKEN:ATTRIBUTE_1)} ).

After enough editing and saving of the token fields, the attribute will eventually update in the invitations. It's almost as if the e-mail template engine is using an internally cached value for the attribute that is either stale or may not be initialized yet (in the case of freshly added tokens or token attributes).

Surveys do not have this issue; they seem to update immediately if the token attribute is edited.