I have seen rates disappear from at least 4 different sites after I've filed successful LNF claims. In one case the next morning, but usually with a bit more of a lag.

It's easy for me tell because (as I explained in more detail above, in post 22) I tend to need to stay in the same area again and again and again and again, so I keep checking for LNFs in the same area repeatedly, first obviously trying what's worked before.

In fact, of 5 sites I've used for 4 Marriott family hotels in one area, only one of those 4 hotels, at only one of those 5 third-party sites, has kept their LNFable rate up on an ongoing basis for months.