Crossed posts again.
The witnesses don't even know that the document they saw you sign was your will, yet alone where you'll be keeping it.
As I wrote above, the two people who witnessed my own will were just a married couple that I happened to be working with on one particular day several years ago. I've never seen them since, although I do know that at least one of them has since passed away. (That doesn't invalidate their signature).
Obviously it makes sense that somebody should find your will after you've died, so many people would choose to tell the executor(s) of their will where they've put the document. However, as long as somebody will find it [and then pass it on to the executor(s)] it's not essential.
I've not yet told the two executors of my will (who are also the main beneficiaries of it) where I keep it but it's on the very top of the contents of the drawer where I keep my important documents (such as my passport, etc) in an envelope with 'WILL' written in massive letters, so it would be hard to miss by anyone clearing the contents of my house.