At the end of each month we see a lot of complaints that Free/Busy publishing isn't working because users can only see the next month's free/busy information.

It's working, but Outlook uses this month and next month as the two months that are published by default. If users want to see "farther out" as they approach the end of the month, they need to change default to 3 (or more) months.

Each user needs to change their free/busy publishing in Tools, Options, Calendar options, Free/Busy. Changing it on your machine will only affect what others see when they check your free/busy, it will not allow you to see more of your co-workers free/busy data.

Don't publish a high number of months unless your co-workers routinely need to see free/busy data that far out and don't update more often than 15 minutes unless it's absolutely necessary.