In principle you could certainly use the gate as a storage or stasis device, converting people into matter and then reintegrating them at a later date.
I don't see any reason why that should result in them becoming 'younger'.
The stargate basically works by converting matter into its constituent atoms, sending them via a wormhole to another location and then re-converting them into conventional matter.
In the episode "48 Hours" we see Tealc trapped inside the gate itself until they can create a fake wormhole horizon and basically trick the gate into reintegrating him.
Carter explains the principle quite nicely;
CARTER : You know how the Stargate turns matter into energy and then
transmits it through a subspace wormhole?
DANIEL : That's gate travel 101.
CARTER : And the gate on the receiving end is what translates the
energy signature and reconverts it back into its original form.
HAMMOND : Major!
CARTER : The Stargate has massive amounts of memory inside it. It's
like a computer buffer. It temporarily restores the energy patterns
before it reconverts them into matter. Now it does this to make sure
it has all the information before it reassembles the object - or in
our case, person.The error we're receiving from the gate seems to
indicate there's still an energy pattern stored in the memory buffer.
DANIEL : Teal'c?
CARTER : If the Alkesh crashed into the DHD on the other planet it
would have cut off power to the outgoing gate. Then the wormhole would
have been severed prematurely. Now if that happened before our gate
was able to reconvert Teal'c's energy signature back into matter...
HAMMOND : Teal'c is in our Stargate?
CARTER : His energy signature, yes. Stored in the memory.
Rodney and the SG: Atlantis team use the same principle in the episode "38 Minutes" where they do this to Sheppard intentionally. He's heavily wounded and it means that from his perspective, he'll get medical attention immediately
Travellers don't seem to experience any relativity effects while moving inside the wormhole itself (which is actually pretty consistent with the Einstein/Rosen concept of a "bridge" or "gate" between fixed locations in space and time) so the essence is that you don't get younger by travelling in a wormhole, you simply pop in one place and pop out the other. You might appear not to have aged but they don't make time go backwards.