(1) more often than not意为“常常，屡屡”，多用作副词短语，相当于very frequently。

• More often than not he does help us.
  他的确经常帮助我们。
• More often than not he comes over on Sunday.
  他常常在星期天过来。

 (2) as often as(=each time that)意为“尽管多次”，用作连接词短语，引出从句。

• As often as I tried to ring him (up) the line was engaged.
  每次我想打电话给他时，总是占线。
• As often as I have tried to do this, I have always failed.
  我尽管多次尝试做这事，但总是失败。

 (3) as often as not意为“常常”，接近more often than not，用作副词短语。

• During foggy weather the trains are late as often as not .
  在雾天里，火车常常晚点。
• The traffic is so busy there that, as often as not (or: more often than not ), you can't even cross the street.
  那里的交通那么拥挤，经常的情形是，你甚至无法穿过马路。

 (4) often as是“尽管……，常常”，用作连接词短语，引出从句。

• Often as I invite him to our party, he never comes even once.
  尽管我常邀他来参加我们的聚会，他从没有来过。

 (5) once too often可表示“又一次，再一次”，指次数太多，超过明智、安全等的限度而发生问题，招来麻烦。

• He exceeded the speed limit once too often and was fined $20.
  他又一次超速，被罚了20美元。
• You have let me down once too often and I shall not trust you.
  你又一次让我失望，我将不再信任你了。

 (6) every so often作“有时；每隔一会儿就……”解，与occasionally, (every) now and again, now and then, from time to time意思相同。

• He comes to see us every so often/from time to time .
  他时常前来看望我们。
• It was hot, but every so often Susan brought us something cold to drink.
  天很热，但苏珊不时给我们送来些清凉的饮料。