I've been in this situation a couple of times where the first few courses have absolutely flown out the kitchen, asking the waiting staff to slow it down is perfectly acceptable and works. Once was at Martin Beresetegui, at Azurmendi the lunchtime tasting menu I had took hours and was decidedly leisurely without prompting. I don't think they're flipping tables at places like Azurmendi and if they are they should let you know on reserving.