Illustrator will not replace a previous version of a file...adds '01' to the file name instead?

Hello,

I'm having an issue when trying to overwrite a previous version of a file in Illustrator. When I create a graphic for my job, I often have to export it to a compatible format to pass on to colleagues for review, and then go on to make revisions and re-export the final version (usually PNG).

The issue is that when I am exporting/saving the final version, I typically want to replace the old version (as it's now obsolete...) and so I click on it to 'inherit' it's file name. Illustrator then issues a warning asking me to confirm if I would like to replace that file, which I do, but then it saves the new version as a separate file anyway? The file name is that of the older file I was trying to replace, with a '01' tacked on to the end of it. If I make 2 or 3 revisions to a design I end up with file names like 'Sample-01-01-01'...

Makes it very frustrating to manage which versions of my files I should be keeping or culling...so if there is something glaringly obvious which I'm doing wrong and someone could help me out that would be great, thanks!