The driver currently allows a value of 0 for maxStaleness, which it documents to mean "no maximum". This is unnecessarily confusing, as users might thing, despite the API docs, that maxStaleness of 0 means "totally fresh".

Consider changing the ReadPreference API to not treat 0 specially, and require either:

• use of overloaded factory methods that don't take a maxStaleness parameter to indicate that there is no maximum
• use boxed Long so that null can be passed as a value, and don't treat 0 specially.