I have worked for a long time to set up my new speakers optimally. Yes, I got good sound relatively quickly, but there were still gains to be had (and I'm not certain that it's completely done yet either).
There is no way some expert can come in and set up things perfectly in two days, especially in a room that is as difficult as mine (even an industry designer who visited found my room surprisingly difficult, especially in the bass). Yes, they can be faster than me, but to get to the level of fine-tuning where I am at now is impossible in a few days. You have to actually live with the system, get to know the sound in the tiniest detail based on a good number of recordings of very different music, which takes time, know exactly what *you* want per your own personal taste, and in the process tweak here and there accordingly.
Also, I needed to acquire extra acoustic treatments just for the new speakers, change the amp stand etc., which are all tools and procedures that would not be available to an external set-up guy during a short visit.