问“long before 与 before long”有什么区别?

例句：
The house was burnt to ash long before the fire fighters came.
The house was set on fire.Before long,it was burnt to ash.
第一句before long表示在消防队员赶到以前房子早就被烧成灰烬了
第二句before long就是过了没多久
可以理解吗?