As for spares, it's not a problem. Everything is easily available and much is shared with the 2.1TD (surprisingly). Whilst it would be nice to hold spare rams, if they're not leaking, they're not going to suddenly fail and spheres, although specific, last as well as any other Xantia and if push comes to shove, spheres from other Xantias can be used. Remember an Activa is just a Hydractive Xantia with some additional bits on it.
As for spares that are useful to keep in, I keep an aux. belt, strut leakage return pipes, hydraulic seals and a height corrector link. I also keep brake pads, filters and 5 litres of LHM on the shelf along with a selection of fuses and relays. I travel with a good emergency toolkit.
So go out and enjoy it! Look after it, give it regular TLC but don't wrap it in cotton wool...
