Do you have some extra process that makes this happen? I don't remember anything in the version of kanban I saw that implied the lead developer should be doing this.

> Manage by exception. If most cases just take a few days, set up some kind of system to mark the outlining cases out. Then you can investigate and address these exceptional cases if required.

In the project I'm thinking of it wasn't a single exception; rather the length of a typical task gradually crept up (from below 2 weeks at the point when we switched from scrum) until it was normal to have tasks lasting multiple months.