at long intervals

例句：

1. 1.They have been apart for a long interval.
   他们分开已经有一段时间了。
2. 2. The book was published at great intervals.
   这本书出版的时间间隔很长。
3. 3. He had to wait at great intervals before he could see his friend again.
   他不得不等待很长时间才能再次见到他的好朋友。