Jim doesn't have any problems with Walter getting even closer than he pulled him up to be before, so If anything now they're in the prime state to just drift off.

Unfortunately for Walter, even his super fast thinking isn't fast enough to catch Jim before he actually falls asleep again, the hours of being awake stacking up too high once again; but Walter will get the feeling that it doesn't matter that much.

Jim's slowing heartbeat and comfortable hold around Walter's waist might be what he wanted, anyway.