Serum 207s actually mix faster than normal potions. They mix as fast as making unfinished potions, which is one every 1 game tick (.6 seconds) rather than one every 2 game ticks for a normal potion (1.2 seconds). Doing a little math, you spend 8.4 seconds mixing an inventory of 14 serum 207s (while you would spend 16.8 doing the same with other potions). If you take around 6 seconds to bank, that's 3500 potions mixed per hour. That's noticeably faster than normal potions, which is 2210 per hour. Note this is if you take 6 seconds to bank and waste no time in between. Realistically, the numbers are likely to be a bit lower. Remember that is one step alone. If you are making the unfinished potions first, it will take twice as long, so you could make 1750 unfinished potions, and then serum 207s, in an hour.