drupal_get_breadcrumb() can be expensive (can invokes various menu perm callbacks). We should avoid calling it unless necessary.
Is that really a performance improvement? If you look at the code in drupal_get_breadcrumb() it calls drupal_set_breadcrumb() to get the data and that function does the heavy lifting once, storing the result in a static variable which is returned on subsequent calls.
So no matter how many times you call drupal_get_breadcrumb() the performance hit after the first time is next to nill.
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