Technically there may be no "safe distance" at all, depending on how much time you're talking about. The whole galaxy seems to be caught in the spiral of a super massive blackhole, and it's just a matter of time before everything falls into it, although most stars will probably die out before they do. So I guess you could consider that "safe", since the time it takes to fall into the blackhole is longer than the time the object itself exists. Whole galaxies are probably drawn to each other, too, like we are to Andromeda and Andromeda to us.
It deserves mentioning that it is very difficult for things in space to fall into each other. If two bodies aren't on a direct collision course they will orbit or slingshot, not "circle the drain until they fall in." The effects that do promote "falling in" happen on very, very long timescales with respect to anything, including stellar lifecycles (you mentioned this but didn't emphasize the extent to which one timescale utterly dominates the other).
We are used to circulating fluid inevitably falling into the center of a drain, but this only happens in our daily lives because viscosity allows the water to shed angular momentum (about the drain) to its surroundings. No angular momentum transfer = no falling into the center, and a galaxy doesn't have a gigantic porcelain fixture anchored to the central black hole to which stars can transfer their angular momentum :)
Actually there is a way that objects orbiting other objects can shed angular momentum: emit gravitational waves. We've observed this with binary pulsar systems; it's expected that it would also be taking place with objects orbiting the black hole at the center of our galaxy. This is one of those "long timescale" effects in most cases, but for objects close enough to the black hole at the center of our galaxy its time scale might not actually be longer than the lifetime of some of those objects. (That would only be true pretty close to the hole, though.)
The whole galaxy seems to be caught in the spiral of a super massive blackhole, and it's just a matter of time before everything falls into it
That's not necessarily true. From far away, a black hole is just like any other object with the same mass; there's no extra ingredient to a black hole's gravity that makes things more likely to fall into it from far away.
The central supermassive black hole does consume the galaxy, but in fact the rate of consumption is so excruciatingly slow that the galaxy will have "evaporated" long before then. Random processes like collisions with other galaxies will eventually eject nearly all stellar remnants into intergalactic space. The central black hole will only end up consuming about 1% of the galaxy's stellar remnants (as you say, all stars will have died trillions of years before the galaxy evaporates).
The Milky Way is fated for just such a collision with Andromeda in a few billion years, and there's a chance our solar system will be ejected!
Well, I was told by an astrophysicist on /r/askscience, that inside of 1.5x of the event horizon, there are no more stable orbits (you either go hyperbolic, or fall in). Outside of that distance, you can absolutely orbit a black hole just like any other body, with the same chances of outside forces influencing your orbit.
He shouldn't have used the word "stable". Orbits from 1.5x the horizon radius to 3x the horizon radius exist, but they are unstable, like a pencil balanced on its point; any small perturbation will cause the orbiting object to either fall into the black hole, or fly off to infinity. Orbits at 3x the horizon radius or larger are stable in the sense that small perturbations do not do this; the object will just tend to adopt a slightly different orbit.
Since the post I was responding to used the word "safe", I was not including the orbits from 1.5x to 3x the horizon radius, since they are not, IMO, "safe"; you'll need rocket power continuously available to avoid falling into the hole or flying off to infinity due to small perturbations.
(A link to the askscience thread would be nice, btw.)
