Rebuilding Post Cache

[Relientk]

I recently ran Cleaner.php on a old impex import. All was successful with the clean up. I would like to proceed to do another impex import but here is my dilemma:

it says-

Once cleaner has been run successfully you must rebuild the Rebuild Post Cache in the AdminCP > Maintenance > Update Counters

Rebuilding the post cache takes such a long time (hours) my question is this-

Because I plan on doing another import with impex can I go ahead with that import and then run the cleaner again and then rebuild the post cache?

basically can I do the rebuild post cache only once?!

Or do I need to run it twice once before the second import with impex (since cleaner was just run now from an old import) and then again after the new import?

Thank you in advance for any help regarding this!

Thank you!