As already pointed out, many factors affect this: recording, system, room, positioning, etc. There is no single "right" or "wrong" answer as to where the soundstage should begin and end. Many people, I among them, appreciate layering, which is enhanced with a deep soundstage, wherever the front plane of that soundstage may start. Very broadly speaking, the more you pull your speakers out from the wall behind them, the more likely you are to achieve front-back depth of soundstage.
