Starting with a new database:

> db.cstats.ensureIndex(

{ "Date": 1 }

,

{ expireAfterSeconds: 10 }

)

> db.cstats.insert(

{"name": "test1", "Date":Date()}

)

> db.cstats.find()

{ "_id" : ObjectId("506f11bc9bf1fda81870da0a"), "name" : "test1", "Date" : "Fri Oct 05 2012 09:58:36 GMT-0700 (MST)" }

This doc never gets deleted.