1. 现在完成时影响性用法是否大多为瞬间动词？
是的，现在完成时影响性用法动词大多为瞬间动词。如：
We have saved some money against old age. 我们已存了些钱防老。
We have named a date for the party. 我们已定好聚会的日期。
Traffic accidents have caused many deaths. 车祸招致了许多人的死亡。
Many businesses have closed down because of the recession. 因经济衰退许多企业纷纷倒闭。
为什么现在完成时的影响性用法大多为瞬间动词？因为，延续性动词的现在完成时通常为持续性用法。如：
He has been in teaching for 20 years. 他从事教学已经20年了。
I have lived in the south for years. 我在南方已经住了多年了。
He has worked in this same school for 30 years. 他在这所学样已工作30多年了。
但以上说的只是一般情况，例外的情况也是有的。如：
I have known him since we were children. 我们从小就认识。（现在完成时表持续性用法）
You needn’t tell him the news. He has already known it. 你不必告诉他这个消息了，他已经知道了。（现在完成时表影响性用法）

2. 瞬间动词还有哪些特色用法？
瞬间动词指表示动作极为短暂的动词，如hit, jump, tap, knock等。现在进行时用于少数瞬间动词表不断重复的动作，如：
The boy is jumping with joy. 那男孩高兴得在跳呢。
Someone is knocking. 有人敲门。
The baby is kicking and screaming. 小孩儿踢着嚷着。
除上述例句中的jump, knock, kick外，瞬间动词还有hit, nod, tap, wink, cough, shoot, drop等。主语如为复形名词，某些动词的现在进行时往往有“不断”或“一个接一个”的含义，如：
People are dying in that part of the world. 在那个地方人们不断地死去。
Men are dropping with malaria, dysentery and simple starvation. 士兵们由于疟疾、痢疾或仅仅因为饥饿一个接一个地倒了下去。
但有些表示短暂动作的动词的现在进行时并不表动作的重复，而是表动作的开始。如：
The ambulance is arriving. 救护车就来。
The weather is clearing. 天晴了。
The sun is setting. 太阳开始落山了。
I’m finding that this problem is more complicated than I had expected. 我慢慢觉得这个问题比我预想的要复杂些。
You’re young people. You ate only beginning to live. 你们是年轻人，刚刚开始生活。
有些动词的现在进行时则表动作即将结束，如：
He is dying. 他奄奄一息了。
I am finishing. 我快做完了。
It is ceasing to rain. 雨快停了。
The fruit is ripening. 这果子快熟了。