On a server with a long respawn timer, reconnect before the timer finishes.
This lets you avoid the timer. Apparently.

Why would anyone want 30 minute respawn timer server OPTION?
On my favorite vanilla server (100% vanilla settings, loot economy and no mods) the meta gameplay strategy is to make many hidden quickly accessible stashes and if you are killed run straight back into the fight (which killed you) after respawning, with a stash gun.
Or simply run back to your body before your killer can loot it, then kill your killer even though you got defeated earlier.
This happens every time I have a fight within 3 kilometers of the coast (huge portion of the map) ON THIS SERVER and is replicable on any vanilla / official server.
Just recently in Zeleno we wiped multiple squads, and every time before we could even loot all of the bodies the squadmembers had already respawned and returned, the top time was around 10-15 minutes after death.
Sometimes even with high end guns.
You can't even loot the body you killed INLAND at a higher tier millitary area before the guy shoots you in the back with his own corpses loot sometimes.
At the spawn towns this problem is amplified by a million.
DayZ "survive at all costs"? More like DayZ you have endless lives and an infinite arsenal.
DayZ game genre? Re-spawn arena shooter. ;)
A long respawn timer OPTION for server admins would completely fix this.