Can't tell much from mine (only ~73K so far), but I've never had any head gasket problem prior to 200K (original engine) - Here'a a few stats:
. '83 Supra (5MGE) - 180K (sold to a friend - now has more than 250K)
. '83 Cressida (5MGE) - gave away @ ~345K
. '87 Supra Turbo (7MGTE) - 207K...