If you're unlucky (as I think I mostly was), you'll only get one star per level, making it impossible to raise a pokemon from 0 friendship to max between updates (also assuming that you stop at level 999 as I did).

With the current 29 non-event pokemon that can rotate through the customer base, even running all 999 Master Cafe levels means that you may see a pokemon 34-35 times, on average. However, after completing 999 levels, my whimsicott was only barely at level 3, and my emolga was only at 20/48 stars in the second level of friendship. I figured that this should be doable based on early gameplay which allowed me to max out new staff members with one or two runs of the original 300 Master Cafe levels. It was my second attempt (my first attempt ended in the 980s, and I had to give it a few weeks before trying again), and I was using the challenge as a means of raising my whimsicott from early level 2 up to level 3 as well as trying to max out the newly acquired emolga. I made a run at level 999 in Master Cafe mode this round of updates. The diverse mix of pokemon makes it difficult to raise them to levels beyond joining the cafe staff, and new avenues to leveling up staff members is required to rebalance player ability. Current state of Cafe Mix creates a daunting challenge for new players to get beyond the standard cafe levels.

Pokemon cafe mix emolga