Answer:
a:: At -80 deg C allograft skin can be stored for months and at liquid nitrogen temperature (-196 deg C) allograft skin can be stored for years.
b: You can get AIDS for allograft skin. The first report was in England from unbanked skin.
c: Extra STSG can be stored for years if prepared properly. Skin strips are rinsed in phosphate buffered solution and placed in cryoprotective medium like LR, 15% glycerol, 40 mcg/cc gentamicin, 100 mcg/cc PCN, 100 mcg/cc streptomycin. After equilibration at 4 deg C for 120 minutes, the skin is cooled at 1 deg C per minute to -196 deg C, the temperature of liquid nitrogen.