Consider yourself lucky; bonuses are becoming more extinct for other than management.
You may want to use your bank's benefits book to define what the benefits are for part-time help. In our case, it is one-half of what a full time person receives.
Benefits are usually figured on the group, and not individually. In most companies, it would be too difficult to recalculate the average workweek, and pay those benefits. For fairness to all, it’s uniform on what the minimum requirements of the position are. It’s also easier to prove to the EEO should someone file a complaint – everyone was treated the same.
It does seem unfair if you are an overachiever, but when you get ready to go full time, there will be many managers who want you on their team.
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Integrity. With it, nothing else matters. Without it, nothing else matters.