The UK film magazine Sight & Sound has been going since the 1930s and has changed its masthead more times than I change my shirts. At first I thought they changed them every decade, until I noticed there were three different ones in the 1970s. The magazine was very wordy for a long time up until the 1970s and 80s, but by the 1990s it drastically changed, turned monthly (rather than seasonal) and became a lot more visual, which makes sense for a film magazine. Even so, a magazine like Variety, say, has had the same masthead for about a hundred years. I don't mind a new masthead every few years but Sight and Sound's lack of a strong visual identity (it looked awful in the 1980s) is a problem for a visual-based magazine. Still, it's always been my magazine of choice.
From top to bottom: 1951; 1969; 1971; 1973; 1978; 1983; 1992; 2000; 2002; 2009; 2014, its current incarnation.