For a group of folks who eschew material goods, a pair of Birkenstocks is a significant investment. Many hippies who do not wash their hair will go to great lengths to extend the life of their footwear.
The cork and soles can be damaged by exposure to concentrated heat. Do not leave your Birks in the minibus at Burning Man, and keep them away from the communal bonfire at night. If your shoes become wet while you are cavorting in a stream, allow them to dry slowly, away from sources of heat.
Don’t wait for your soles to wear down to the cork. Have the soles repaired when they have been worn down to about 1/8 inch, before the cork is damaged.
If you walk on the beach in your Birks, be sure to immediately wash off the salt-water residue with fresh water to avoid corrosion.
Many a hippie has left his Birkenstocks on a porch, beach, or youth hostel stoop, only to have them pinched in short order. If you leave your shoes behind, at least hide them under a towel, bury them in sand (but mark the spot so that you can find them later), or cover them with branches.