Some brands maintain grille design themes over many decades. These are usually high-price makes, and many owners seem to enjoy the fact that people seeing their car know that it is indeed a prestigious brand. Examples include Rolls-Royce, Packard, BMW and Cadillac.
General Motors' Buick brand has had a mixed history so far as grille theme consistency is concerned. From around the mid-1920s through the 1940s, the upper shape of the hood and grille was a sort of double hump (see the 1942 image below for an example). For 1939, Buick added vertical bars in the grille face that were abandoned for 1940 and 1941 and then brought back for 1942. These vertical bars then became Buick's dominant facial theme until the mid-1950s when other themes were tried. But the vertical bar theme was a strong identifier, so some -- not all -- Buick models in later years continued to use them, often in a subtle manner. By the 1990s, vertical grille bars returned as Buick's main identification theme.
The images below sketch what happened.
Whereas the 1939 grille had thin vertical bars, the 1942 version was given a toothier look, setting the theme for the next nine model years (there were no 1943, 1944 and 1945 models produced due to World War 2).
Post-war Buick grilles retained the bold bars while the ensemble's shape was downplayed, reduced to the shape of the plate holding the Buick crest.
Here is the infamous ultra-toothy 1950 grille. The previous shaping is now abstracted to character lines on the hood.
Bowing to criticism, the teeth over the bumper style was quickly abandoned. The shrinkage of the bars was slightly compensated by enlargement of the "bullets" on the grille's edges.
Oldsmobile, Buick and Cadillac received new bodies for 1954 that seemed futuristic at the time. The most radical feature was the panoramic or "wraparound" windshield, a fashion that remained in effect for the rest of the 1950s. Buick's grilles, on the other hand, were simple and understated. But Harley Earl or Buick management must have decided that the vertical bar theme had been around long enough, and something new needed to be tried.
So bars disappeared for 1955, being replaced by a mesh.
Then in 1956 the mesh pattern was changed and the grille was slightly V'd in plan view, an extension of a crease on the face of the hood.
But for 1957, bars returned. This time as very thin form.
The next model year produced a radical change. The many thin bars were replaced by many little freestanding, indented squares. Other grille schemes were used over the next 30 or so years, some using vertical bars, others with different patterns.
As was mentioned above, by the 1990s Buick returned to its tried-and-true grille bar theme. Shown here is a recent iteration.