This is going to vary considerably between drive manufacturers and to a lesser extent drive models. Unfortunately there aren’t many experts on this subject, and the forum with the most discussion about drive firmware (rpc1.org) closed last year.
I don’t know about TL7, but I have concerns about this from a preservation and long-term maintenance perspective.
When firmware can be downloaded, the file that is flashed to the drive may not contain the drive’s complete firmware. Any small or large region of factory programmed code and/or configuration that is unchanged during the life of the drive (and skipped over by flashing tools, the drive internally, or both) may be essential for the drive to function. In the event of a failure of the flash chip, the drive becomes unusable unless it has been fully backed up.
Of course, not all firmware can be downloaded. Yes, there’s a nice archive for older drives on what’s left of rpc1.org, but if I remember correctly they only plan to keep that archive up for a few years. The Internet Archive’s Wayback Machine of course also has lots of old firmware on it too. More recent firmware may be more of a problem for the Wayback Machine though as sites tend to shy away from linking directly to the firmware download files. Pioneer’s FW is still eventually getting picked up even through a license agreement page which is nice (although not all of the latest stuff has been picked up yet). LG’s FW is not being picked up at all as far as I can tell.
In addition there are devices that never received firmware updates or pre-dated the Wayback Machine.