$ node test2.js
total keys (before): 7
total keys (after): 304
$ cat test2.js
var bluebird = require('bluebird')
var bp = bluebird.resolve()
console.log('total keys (before):', Object.keys(bp).length)
for (var i = 0; i < 100; ++i) {
  bp.then(function () {})
}
console.log('total keys (after):', Object.keys(bp).length)