Bonus for Property Mangager

[Jan Willinger]

How much is an appropriate Christmas bonus (personal, not payroll) for a property manager?  Is it based on number of properties, revenue generated, amount paid or some other factor?  I have five properties (10 tenants) in another city and my manager does a great job, involving me very little. I also have someone managing two properties (two tenants) in the city I live in.   Any advice will be appreciated; can't seem to find anything online.  Thanks!