replacing a previous package verson

[Andrew Schulman]

After all this time I feel that I should know the answer to this, but here
goes.

I have fish-3.4.1-1, a bugfix release. I want it to replace fish-3.4.0-1,
leaving fish-3.3.1-1 as the previous release. 

What's the best way to do this? Should I create override.hint, with 

keep: 3.3.1-1
replace-versions: 3.4.0-1

? This seems as though it might be right, but one question I have is, will
override.hint persist in future releases unless I replace it?

Thanks,
Andrew