Not as often as I'd like or "nightly" as some of their promotional media has stated, (at least for the 10 course) we planned to go there on our trip last month in QVR and asked they send us the menu for QVR when we confirmed the reservation and it was nearly the exact same menu as when we went in October of 2015 and had the 10 course in the main dining room and although they stated they could change a few of the dishes but most would remain we opted to cancel instead of dropping ~2K on a table for 4 for pretty much the same meal we had two years ago.
Personally the more I think about Victoria and Albert's the more it's tough to rationalize going. I could go to Flying Fish, Monsieur Paul, and Citricos (all including alcohol) for the same price as going to Victoria and Alberts with the 10 Course with reserve wine pairings and a non-caviar, non-truffle supplement or two.
We did have a different meal between December 2013 and October 2015 but the 10 course menu was still the same as it was in May 2017 as October 2015