What other ways are there to save a human for a very long time. I know only about cryostasis. Let's say we have a spaceship traveling several hundred light years to a distant galaxy.
If you really want to go to a distant galaxy you should first realize the nearest (Andromeda) is about 2.5 million light years.
If You really want to travel that far (and get there before your ship falls apart) I think the best is "just" to exploit Lorentz time contraction.
Have your spaceship to travel very near to light speed (say 0.99c) so that the crew would travel ~7.3 light-years in a single (subjective) year.
Going even closer to light speed effect would be more relevant (at 0.999c in a single year spaceship would travel more than 22.6 light-years).
At that speed you really need to start paying attention to the road ahead, so having an active crew (not in hibernation) may be actually useful.
Digitize and replicate.
Why waste space for storage and preservation on a long journey when you can digitize the occupants and replicate them upon arrival. Any sort of stasis system is going to be complex and require ongoing maintenance power. The advantage of digitizing and replicating the passengers is that all the complex machinery can be left in a powered off state for the journey.
In the ring world books some ships would carry a singularity device. In case of a drastic deceleration (hitting a planet) the cockpit is enveloped in a stasis field.
Inside this field time stand still, avoiding any aging or damage to the material inside.
Another way might be to genetically engineer an immortal human.
Lobsters are thought to be biologically immortal, which means they won't die unless they are killed.
It would be challenging, but at least it's not theoretically impossible.
The Mi-Go have been helping humans travel to Yuggoth for a long time! Their method (from Lovecraft's The Whisperer in Darkness):
There was a harmless way to extract a brain, and a way to keep the organic residue alive during its absence. The bare, compact cerebral matter was then immersed in an occasionally replenished fluid within an ether-tight cylinder of a metal mined in Yuggoth, certain electrodes reaching through and connecting at will with elaborate instruments capable of duplicating the three vital faculties of sight, hearing, and speech. For the winged fungus-beings to carry the brain-cylinders intact through space was an easy matter. Then, on every planet covered by their civilisation, they would find plenty of adjustable faculty-instruments capable of being connected with the encased brains; so that after a little fitting these travelling intelligences could be given a full sensory and articulate life—albeit a bodiless and mechanical one—at each stage of their journeying through and beyond the space-time continuum. It was as simple as carrying a phonograph record about and playing it wherever a phonograph of the corresponding make exists.
No doubt the human brain in its case is protected from free radical damage and constant degradation caused by movements of the body - and so is practically ageless. Encased brains can be connected to temporary artificial bodies as needed for various purposes - humanoid or otherwise. Much of the time these individuals occupy themselves in virtual landscapes, freed from the constraints of the physical.
Recently in the field of quantum physics, the plausibility of teleportation was elevated with the discovery of Quantum Entanglements.
With this science in mind, you could either teleport your human or save his state. Using a Quantum computer and one heck of a memory device you could save the entire atomic state and structure of a human body off into some storage. Upon arriving just reassemble the entanglements. This would preserve the electrical state of the brain though you would inevitably raise questions like:
What do you do with the original?
What does this mean for the human soul?
Cryostatis Pro: we (of september 14 of 2017) are doing this every single day, at least in first world countries. So the techonolgy already exists.
Con: the frozen water expands bursting cells open thus killing the thing you want to perserve.
May i introduce you to the Medical Nanobots. tiny little robots, nanobots (in fiction at least) serve many different roles. This specific role is to make sure the chemical-horomal balance of humans in statis allows them to "Crash Wake" (aka OMG THE SHIP IS FALLING APART BECAUSE REASONS! WAKE UP NOOOWWW!) in emergences.
The nanobots will of course make sure your passengers get enough stuff to survive the journey and may double as DNA Repair Systems for radiation treatment. (Example: https://m.youtube.com/watch?v=7401A3k7OYc)
Sure the end product may not be Genetically human. But it got them there didn't it? Also this allows for a sub plot on what it means to be human.