I have a bunch of letters both to and from my grandmother from the early post WW2 era. She was Belgian, and moved to Canada in 1946 with my grandfather who was a Canadian soldier in the war.
The letters are all written in Flemish, so I have no idea of their contents, but I imagine they are mostly updates on the family, missing you, births, marriages, etc.
My question mainly is whether these are of any historical use to anyone? I know in my own studies of my family history I've found such things useful, but is this something that would be worth archiving? Should I keep them and pass them down? Or just toss them away given their likely superfluous contents?
Please don't throw them away! A massive problem for historians trying to study the day to day lives of people outside the ruling classes of society is the lack of written documents concerning their lives. The problem is, as you have said, that people regard these letters as superfluous due to their content and don't bother preserving them or just throw them away. This leads to a shortage of actual primary sources that we can use to find out about the day to day lives of ordinary people. Letters between ordinary people are a useful way of finding out about how they lived, what things were of greatest concern to them (usually mentioned frequently in letters or often at the beginning) and what relationships they had. It might be worth trying to find someone who can do a proper transcription and translation and give you a better idea of what the letters say. I'm sure future generations of your family will be fascinated to read about their ancestors lives and to have such a physical link.