Hi I work 30 hours a week and I do extra duties to cover my managers holiday as I am the duty manager. We now have a training duty manager who is working with us temporarily until April and she works 37 hours a week. So my manager is on holiday in 3 weeks time and doesnt want me to do extra duties because the trainee is there for cover, however as soon as she leaves my manager is expecting me to do all the covering again. I feel abit unfairly treated. Is this fair?