Add timestamps and expiration to mongoose schema

mongoose-timestamps.js

var schema = mongoose.Schema({
    email: {
        type: String,
        required: true,
        lowercase: true,
        index: {
          unique: true
        }
      },
    expireAt: {
      type: Date,
      /* Defaults 7 days from now */
      default: new Date(new Date().valueOf() + 604800000),
      /* Remove doc 60 seconds after specified date */
      expires: 60
    }
    /* Automatically add createdAt and updatedAt fields to schema */
  }, { timestamps: true })

i would like to set the expiration time when the schema get created no a default one !!