Type collections don't just contain common coins!! (I speak from experience..). Also, I do have date runs for a few favourite series, e.g. George V halfcrowns 1927-1936, and bronze pennies 1895-1967, though I don't lose any sleep at all over the odd gap such as 1914 in UNC, but I would love a high grade 1946 ONE' penny so I do take your point about filling gaps. But as I say, I really don't lose sleep over most gaps I have.