Width is why “WWW” runs out long before “iii”. A title in capitals or with wide letters can be cut far sooner than one with narrow letters. Truncly lays your text out in Arial at the sizes Google uses and shows the exact word where it ends.
Fitting the width doesn’t guarantee Google shows your text as written: it often rewrites titles and sometimes shows text from the page instead of your description. A title that fits removes length as a reason.