>>1226888You can make a sourdough starter before heading out. With proper treatment the starter is alive indefinitely and making breads with it regularly contributes to its health. It needs no special refrigeration. So with sourdough there is no real "expiry date".
If you are making beer similar considerations apply, you could equally do all your bread with barm from brewing and dispense with a sourdough starter. The mass of grain you need to brew and extra gear needed for that might go against the spirit of OP, it really depends how much room you have. Brew gear sterilisation in a no-resupply situation might be tricky, so the failure rate will exceed modern homebrew expectations.
