Game Freezing and Crashing when Playing World for More than an Hour

When playing the game for more than 30-60 minutes, the performance significantly decreases, resulting in visual lag, and in game lag (delay breaking blocks, picking things up, animals stop moving.)

Occasionally, mobs will freeze while the player is able to move, sometimes for a very long time (1-2 minutes). During one of these freezes, I quit the game in hopes of remedying the performance issues, which led to the game being stuck on the "saving world" screen, stopping responding, and eventually crashing. When reloading the world, I was put back a few minutes in a different part of the world I was at earlier. Items, maps, etc were rolled back to that point.