Never! In over 2 years of working, unless there has been a rise in basic minimum wage etc. Your job prospects and salary are not determined by how hard you work and how good you are at your job, but how friendly you become with managers and supervisors. Individual feedback and appraisals do not happens unless there is a complaint about you and you are told.
Pay is reviewed according to law changes, and increase in responsibilities, though the pay does not equate to the level of responsibility. Performance reviews are a rare occurrence,
Every 3 month
Far, far too often for it not to be suspicious.