LensRentals do all possible repairs internally, so I suspect that the downtime on an expensive lens like that is minimal if possible. Roger mentioned on the photography subreddit that the aperture replacement was a $200 part and 3 to 4 hours -- it only took so long because it was that tech's first time replacing that part.

https://www.reddit.com/r/photography/comments/6xg8a7/lens_re...