Actually, if I could piggyback on this discussion (and hope none of my players pop in here to read this)
I'm fully cognisant of juvenat treatments, the age ranges of various Space Marine chapters and well-to-do Inquisitors and AdMech and the like, but I've got some details for an NPC I'm trying to hash out and this discussion ties in with that.
I have a planet that my RT and his crew are going to visit - the planet is inhabited by a tribal offshoot of humanity, who are the descendants of a crew from a pilgrim ship that crash-landed on the planet nearly 2000 years before. I was planning on the remains of the crashed ship having been gradually subsumbed by the planet until it's now just another geographical feature (A forest-covered mountain), with a strong taboo against anyone approaching or entering the "cave system" of said mountain.
Why? Because when the ship first crashed, a surviving Tech Priest went a bit cuckoo-bananas, was trying to repair the ship or salvage what he could, decided the other survivors were trying to sabotage his work and destroy his Machine, and he set battle-servitors of various stripes up to patrol and guard the ship, and make tasty gibbets out of anyone who approached. Warnings about "Don't go near the ship, the Tech Priest has gone mental and is murderating everyone" have gradually become legends over time about ghosts and demons in the heart of the mountain, destroying any who go near.
I would like, if my players decide to try and loot the tasty pilgrim ship (relics and sacred artefacts, yay!), to still have some of the servitors roaming the corridors, and possibly even Señor Tech Bananaphone lurking around somewhere in there. But after 2k years, is that possible? I was thinking the ship would still have minimal background power, so servitors could conceivably be recharging that way - but what about their gooshy human bits? And the TP himself - if he was sufficiently machine-like before the crash (or upgraded himself enough after), could he have survived that long? I was planning on having a stasis-vault on the ship where relics and artefacts may be - can human(oid)s safely use stasis fields or is it for inanimate objects (Hi Rowboat Girlyman) only?