视情况而定.it has been a long time since a serious war occurred in the western world.
it has been a long time since the technology has motivated us to make things.
谓语为过去式的多表示已经过去的,为过去分词的多表示还在持续进行的对现在还是如此的状态.一般中学考试多考虑为第一种.