Fons: a digital camera is much more dependent on the availability of spare parts and electronics than the old cameras of say the '60s. A simple thing as lack of suitable batteries can stop its use even though the camera might be fully functional. If the software support for the camera ceases or what software one uses at present no longer can be installed under new operating systems, you are out no matter what state the camera is in (or you are limited to jpgs, not RAW).
That being said, having old film cameras serviced demands a supply of spare parts that only can be met by skilled repair techs and scavenged and cannibalised cameras. Old camera maintenance won't be cheap.
Luckily, my Nikon D750 has a battery grip that allows the use of AA-size batteries - part of the reason why I chose that model instead of a used D3s which functionally would be top notch. The other part of the reason was supposed higher IQ from the D750 files.
Regarding the software support for the different RAW formats: There I feel rather safe and secure. I refuse to use activation crippled software or subscription based software - both of which would make the user's RAW conversion impossible when the software company ceases to support one's RAW format or activation/subscription is no longer available.
It is beyond me how people can accept such improper behavior as forcing us into dependency on activations or subscriptions in order to access our own data and images. My solution is the best - IMO - the use of Open Source software under Linux. I use UFRAW, RawTherapee and Darktable extensively under Linux.
- In my opinion, we should all respond to activation schemes and subscription schemes by migrating to Open Source software and tell others about this possibility and the advantages that go with Open Source and free software.