I don’t know, but I bet your users do – and your support staff. Don’t you have any support staff? That might be a clue right there.
It’s pretty simple – you need to ask people, preferably before you build, but then as you go along, well into your product’s lifecycle … and on and on. Products come and go; technology becomes obsolete faster than you can shake a stick at it – give yourself a fighting chance and ask your users what they think. Conduct focus groups. Get a temperature of the market. Don’t lock yourself away in the dungeon of assumptions only to find yourself out of luck when you emerge.