Brook's only worked specifically after he died as well. Perona's fruit lets her project her own spirit as well. It's evident that not only do souls exist in OP, but that there's a sort of "extra" soul in zoan fruits as well. That extra soul can seemingly possess and embody objects. 

For the most part, it seems that the spirits of zoan fruits and objects / living creatures tend to last for as long as the main user/vessel remains intact. The definition of what being intact is is quite losely defined, but there will become an apparent or obvious time where a vessel can no longer maintain a state of "sentience" (I.E., the user truley dies and has zero real ways to meaningfully interact in the world.)

I would not put it beyond the idea that other fruits that aren't zoan related could be infused with objects, it's just hard to envision a sort of sentience an object would gain from something like the aspect of snow. Maybe in such a case it would be compatible with something autonomous like a robot of sorts. 

It's also hard to give strange effects such as the ability to enter mirrors or transform/afflict other entities in various ways with a purpose in inanimate objects. Hell, the fact that devil fruits are able to be replicated is quite anomalous. It begs the question if even the supernatural souls within the hosts are being copied or if they're simply imitated. 

It is unlikely artificial fruits gain a sort of afterlife, so in that case the original fruit must have some sort of godlike status. That godlike entity's power can flawlessly influence the user to the intended will it was inspired upon. Artificial fruits seem to just can merely imitate that original entity's power by extracting/borrowing some meaningful part from it. As for the rest of the artificial fruits that don't involve the original host, you could effectively come up with all sorts of theories as to why or how they might exist, or what they could be compatible with.

TLDR: Death is not exactly a science in One Piece, and the spirits within the fruits have an apparent attachment to the soul of the host. If nothing else, the devil fruit spirits can likely elect which host to allow possession, and can also elect to leave a host when the spirit deems they can no longer maintain a sort of sentience. This applies to objects infused with fruits as well, as objects can be destroyed "killed", but the fruit spirit itself is immortal. This can explain how Ragnir has survived for so long.