There are some dynamics that cause problems.
Occasionally, someone is only going to be able to get a carryover line that also allows him to have the days off he needs in the current month. Once he gets the carryover he has to be able to conflict it next month with a line that also works for him in other ways, in order for him to not have to work extra.
Now, if he can't do that, he is stuck. If he drops the carryover or trips to get down to a normal schedule, he is going to take a big hit the middle of the following month. Getting a zero or near zero check can't be fun, so I can understand this guy working the extra.
I don't understand the guys who bid and protect carryover every single month. Seems they are working too hard.
I do understand guys who M/U. They got paid for a trip, dropped it and don't want to get hit with a deduction in the following month, or want to recover that money in the middle of the third month.