WP nonces?

I am testing wordpress out with various themes, etc.

However, I just want to know if you can create a longer nonce key.

For example: example.com/something&_wpnonce=shortsequence

Could change into this: example.com/something&_wpnonce=longermorecomplexsequenceandalmostimpossibletoguess

I guess it can contribute to WP security.

Also is there a way to refresh the nonces, because I am aware that they are cached for a certain period of time. Is there a way to refresh all of them and assign users different nonces.