The rules already mention on pg 74 that players may try a task again if they fail it and it can be attempted again, with time being the only thing lost. I think that to supplement this, and as an aid to GMs who may struggle with how to handle failed rolls on important moments, it would be handy to include a basic table of time taken to finish a task Something like

1 Immediately

2 1 minute

3 several minutes

4 one hour

5 Several hours

6 1 day

7 several days

8 one week

9 several weeks

10 one month

11 several months

12 one year

13 several years

Have GMs pick a time on the table for the task to normally take, and they add or subtract degrees of failure or success from it to figure out how long they take. Add that the GM can also have a maximum or minimum amount of time for the task if he wishes. It's simple, would be a great table for the GM screen, and helps to resolve a lot of different problems that may come up.