Typically, a couple of weeks. Bear in mind that, when you use lemon juice, the half-life of the zestiness that comes from citrus juices is very short -- as in less than a day (that's why so many recipes insist on freshly squeezed citrus juices). So things that depending on zestiness from citrus, like many mayonnaise recipes, will not be as zesty if kept for very long.
So keeping and top-tastiness are separate matters, as it were.
As the saying goes, you can have it all, just not at the same time....