Is there a break in period for a re-tipped cart?

I just set up a re-tipped Shelter 901 and I wonder if there is a break in period.

If so, how does the sound change during the break in and what differences will I hear once its fully broken in?

How long does it take usually?

This would be a question for the re-tipper. Since many times a re-tip is actually a re-build of the cart, depending upon if there is damage within the cart engine, I would think some break-in would allow the cart to perform better with some signal time through it. I dont think changing the stylus would be cause for break-in, in terms of the diamond, but a new cantilever may also need some time to settle as the alloy material would be newly fashioned.

Certainly a valid question to ask. As for sound differences, you should hear a dramatic difference after the re-tip compared to you old cart of course... but the difference due to any break in may be more difficult to hear.
In my experience a re-tip takes almost as long as a new cartridge to get in the groove. The stylus needs to work off some of the rough edges. I just had my Koetsu Black re-tipped
by Sound-smith and I fully expect it to take 50+ hours to get it sounding sweet again. The first few days are painful and ugly. A new Linn Karma I bought new years ago was unpleasant for about 75 hours then became quite magical. Persevere. If your cart sounds like crap after 100+ hours then I would suggest sending it back.