I’m just a pack rat and save everything.
This is how I look at archiving in general. We save everything, as you never know when it’s going to come back and turn in to another job, or more importantly, client service.
As far as clients taking project files, I find this to be a very tricky subject. Some clients ask for it as part of the negotiations up front. Everything goes in their archive, and they can do with it what they want later on down the line. Sometimes, even though they have everything, they still call for revisions or redos, which is great. (Again we save everything no matter if we hand over a copy of the material or not).
There are other times when clients want the project and media, sometimes years later, and it was not negotiated up front. It is kind if a difficult situation to be in as you don’t want to hold too tight and not provide good client service, but you also want the job so you can continue the relationship. There is no right answer. We often fight pretty hard to maintain the project files and therefore any work that comes out of them, but sometimes it’s just not possible.
Sounds like your situation worked out for the best, though. They called and asked for revisions and will hire you to do the job. Kudos!