k i heard that u must stand everyday to really use xingyi in a fight. The only way to develop power is to stand and i heard from one of Kenny Gong's students.
Not the only way to develop power and you can use xing yi in a fight without standing. This is way too simplistic by far. You can fight with xing yi using no internal power only structure and strategy and still beat a lot of people. Adding internal power just makes your strikes more effective. Also you need to learn how to transfer the ability to create or manipulate internal power into using it in a fight, some people with internal power can't use it. If you have a bucket load of "qi" and try to hit someone with it but they move out of the way and slap you in the face then what good is your internal power? (unless you have developed iron face skill of course)
This is pretty much the same discussion as the duration of Zhan Zhuang thread.
Does standing in san-ti build a bridge? What kind of bridge? as in bridging between you and an opponent in combat? No, san-ti is not a guard stance. San-ti is an engaged posture, all your postures within Xing Yi are in fact variations of san-ti the transitions or movements "bridge" between san-ti postures.
For a beginner san-ti standing will develop leg strength, determination, structure and core strength. As you learn to relax into the posture you can hold longer, you begin to develop the same strong structure without the need for external muscluar tension. This development of structure allows you to later "channel" force or energy or mystic juice or whatever you want to call it and this lets you use "internal power" and makes your strikes more effective. IF you learn to be able to use good structure and internal energy whilst moving, evading, using stragegy, reacting etc. then you will be a man my son.
Remember the road is long with many a winding path that leads to who knows where.
Just do what your teacher says and try not to run before you can walk and take anyone's advice with a pinch of salt (my own included).
BTW I like the Lu Shengli article I have his book which has almost identical content. Don't agree with everythign he says but I like his attitude.