It is / has been + 段时间 + since + 一般过去时,从句中的动词用延续性动词和非延续性动词有何

1,用非延续性动词,意思是“自从从句动作发生以来已经多长时间了”.如：It is / has been four years since I came here.我来到这里已经4年了.
2,用延续性动词,意思刚好相反,是“自从从句动作结束以来已经多长时间了.”如：It is / has been four years since I lived here.我不在这里住已经4年了.