Overnight liberties are rare for plebes, and usually granted at the last minute after an unusually good event - say, a big win over Army, or something like that. They may be able to earn an overnight other ways, but much varies by internal company practice and interpretation of overnight/weekend guidelines. Factor in any changes of Superintendent, Commandant, or Company Officer, and what happens this coming year could well be different from this year, last year, or or any other year. Nature of the beast.
First semester, hard to plan for. Sometimes they occur after football games, and we end up with a lot of extra bunkers because it's too far/too sudden to get to other places - and quite often they need to get back in the AM for chapel group/choir, or just want to get started on the homework hanging over their heads, the company boards they have to complete, the pro knowledge quiz they have to study for, the room inspection they have to strip and wax the deck for, the watch they offered to take for someone else...
Second semester and succeeding years are much easier to figure out when an overnight or a weekend is possible.
Trust your plebe to soon figure out how the prized overnight away from Bancroft works. DS#2 will soon find his sea legs, know how to tell DS#1 to come rescue him.