Q:

Is it possible to use "after a long time" or "after a long interval" this way?

I'd like to know if these two phrases "after a long time" and "after a long interval", which I often find in Japanese-English dictionaries, are used a lot. 
I don't want to specify how much time has passed since I did something. So instead of saying 

It's been a long time since I had sushi.
   or
  It's been a while since I saw my high school teacher last time.

is it possible to say

I had sushi after a long time / after a long interval.
  or
  I saw my high school teacher after a long time / after a long interval.

I haven't seen these expressions a lot except for Japanese-English dictionaries.   My question is if these phrases are commonly used in the way I wrote above.  
Also I have one more question: if I say, "I had sushi for the first time in a long time" does it sound natural?  

A:

It's not common to use "after a long interval" to mean "after a long time."  Your sentence "I had sushi for the first time in a long time" sounds perfectly natural.

