keep people in roles for at least the duration of the project release
Whenever possible, keep people assigned to roles for at least the duration of the project release. Avoid elevating transient tasks dealing with disruptions to the status of roles. It follows that the roles should be stable.
Dealing with disruptions should not cause more disruption. Once a role pattern is established, and its communication pattern is established, changing people between roles is somewhat disruptive and changing the roles themselves is very disruptive. It follows that one should not create new roles to deal with distractions when they occur. PatronRole and GateKeeper are exceptions to this rule. See also the risks of ProductiveDistractions and UnproductiveDistractions. Distractions should be dealt with by tasks assigned to existing roles. The outcome of applying this pattern is that people become centred on the main tasks of their role, which should be producing the product (see ProducerRoles) rather than on dealing with distractions. Having roles centred on distractions will have people looking for distractions, and in the worst case, creating them in order that they are perceived to be of value. Roles may need reorganizing for efficiency (see the discussion in InappropriateOrganization); in this case it is best to reorganize between projects or between iterations.