Our standard level of service for translation includes both the initial translation plus post-translation proofreading by a second linguist. Is this level of service sufficient for high quality translation? Would two post-translation reviews be better? How about three, four, or five reviews?
Changes to translations to accommodate the individual language preferences of a reviewer can occur almost indefinitely. Ten rounds of review could occur, adjustments to language occurring with each review, while the translation does not improve in quality as a result.
Each time a translation is proofread by a linguist costs are incurred. Increasing translation costs without improving quality is a pointless exercise. Therefore we decide to draw the line at some point.
In most cases the process of a single translation plus a single post-translation proofreading produces a high quality translation. Additional reviews in the process produce rapidly diminishing returns, if any returns at all.