$.02 wanted: Through vs. Stopped mortises

i am making my own window sashes and window and door frames for a cabin. are through mortises or stopped mortises better than the other for any reason? is one stronger than the other? does the exposed end grain of through mortises make them more liable to rot? deposit your $.02 here. thanks

Yes, exposed end grain makes wood more likely to deterioration from exposure. It's easier for water to get into dry wood through the end grain. This is the same phenomenon as the drying process, where more water leaves the wood through the end grain, and leads to checking at the ends of boards.

If you look at timber frame construction in Asia, and look closely at the joints, you'll see that one reason why you see such elaborate joints in Asian style woodworking is that they are trying to minimize the exposure of end grain, for exactly this reason. That's also why you rarely see through dovetails in Asian furniture.