Normally, file names aren't changed destructively.
On a camera like an Alexa or RED, naming conventions are usually as follows (and are set on the camera to ensure accuracy):
A001_C003_161106
Which demarcates:
Camera A, card 1, clip 3 and the shooting date. Reel IDs will follow after that.
When data wrangling on the day, the wrangler or DIT will have at most basic a laptop with 2-4 HDDs, and the more extravagant the setups, the more RAID arrays start coming into it.
The folder structure will usually be something along the lines of
[Shoot Date] > [Camera Letter] > [Card #] > Clips.
The same data is copied onto all HDDs, and usually checksum checked (using software like ShotputPro) to ensure the data is 100% identical between the cards and all HDDs.
One HDD will be sent to the editor, either at the end of the day (where he/she will likely make their own backup, or insert into their own RAID array), or on lower budgets/shorter shoots, at the end of the shoot. One can be sent to the colourist, and one usually goes home with a Producer and/or Director.
Names will never be changed destructively, because if the data on one HDD is lost, it will need to be recovered from another one. If you rename destructively before import, you will never be able to link the files back up from a second HDD copy in case of data erasure.
Those with HDDs can hang onto the files for as long as they like/need.
When I've shot commercials, usually the production company will have an HDD backup of the entire project (camera originals, and all edit/sound/vfx files) that the client receives, and they will also make their own backup onto an HDD which then gets archived (and the more high-end outfits usually backup onto LTO tape).
Any change of file names at any stage of the process would result in potential issues:
-inability to track down issues and problems - for example, if you have a file sequence out of camera that appears to be missing files, it can be looked into. If everything has been re-named, then it brings in the possibility of human error when re-naming.
-inability to relink media in case of data erasure - at least unless you re-name the back-up files before attempting to re-link (of course keeping in mind they would have to be re-named identically to what they were - character perfect).
-if files are re-named later in the process (for example you have a draft edit that you called EDIT_COLOUR.mov, and used for colour/VFX that you later re-name to EDIT_FINAL_DRAFT.mov), you allow the potential for project files to be unable to re-link to media, particularly if revisiting a project after a number of years, and being unable to remember how you renamed the files.
Most NLEs allow you to re-name files non-destructively in the bin after import if that makes it easier for you to organise (Avid certainly does), and I would always suggest doing that.
In your case, feel free to do what you think is best - I usually keep all originals even after I've transcoded etc. but it can be hard to justify if you're running out of space... Just make sure you back everything up!