I have a similar situation, just resolved differently. I shoot about 400 frames (mostly bracketed though), select and post-process about 40-50, and deliver it to the client as hi-res jpegs. They do want to see all 400+, and occasionally they would ask for additional one or two to be included in delivery. I told them I am reluctant to deliver all 400+ as hi-res files, for reasons others already stated above (i.e., mainly for the possibility to associate a non-edited file, or one badly edited by someone else, with my name). They understand and agree. They just want to see the whole shoot, to make sure there are no views that I considered unimportant and they do. Ultimately, they are going to use just 3-5 for publication, of those 40-50 I delivered. The trick is, however, in the pricing structure. We agreed on price per shoot. Whether it takes me a day or two to shoot, whether I deliver 30, 40 or 50, the price is the same.
In other words, crucial for your situation is to understand why your client wants those extra files. Two possible scenarios, opposite and extreme: one, as with my client, they just want to be sure they (or you) did not miss something. The second one is more sinister: they want to pay to see your expertise on 3-5 examples, than outsource the rest of the shoot to some post-processing sweatshops abroad for cheap replicas of what you've done.
The less extreme scenario, somewhere in-between the other two, is that they are not really sure today as to what they might need in the future, and just want to be able to come back to the shoot and post-process it later. Ideally, in such a situation, they would contact you to finish your own files. If they are scrupulous. If not, off it goes to a sweatshop.
About scrupulous clients/corporations... most of us all have a rather cynical view on that. We know we can't possibly track all future use of a specific time, territory, and use license, especially for global corporations. We might stumble upon a misuse by pure chance, like the US photographer whose photograph was used for supermarket advertising in... Czech Republic (his traveling friends sent him a proof). However, based on a recent personal experience, the death of a scrupulous client is greatly exaggerated. I have an active license with a global corporation, exclusive, world-wide, etc., paid handsomely. Half way through the license, they called and asked for additional use, and offered to pay, not as good as the first time, but still substantially high. That additional use was internal, a coffee-table book, something I would hardly ever come across, except by pure chance.
