gulpfile destroying my life (the update task only fires once too...)

gulpfile.js

var gulp = require('gulp');
var browserify = require('browserify');
var babelify = require('babelify');
var watchify = require('watchify');
var fs = require('fs');
var envify = require('envify/custom');
var source = require('vinyl-source-stream');
var sass = require('gulp-sass');
var concatCss = require('gulp-concat-css');
var gutil = require('gulp-util');

var mainFileOpts = {
  input: ['./js/main.js'],
  output: 'main.js',
  destination: './dist/js'
};

gulp.task('js', function() {
  createBundle(mainFileOpts);
});

function createBundle(file) {
  var b = browserify({
      entries: file.input,
      fileInfo: file,
      debug: true,
      cache: {},
      packageCache: {},
      plugin: [watchify],
      transform: [
        babelify,
        envify({NODE_ENV: process.env.NODE_ENV})
      ]
    });

  b.on('update', function(e) {
    gutil.log('update');
    if(typeof e === 'object') {
      gutil.log(gutil.colors.cyan('Changes detected on: '));
      for (var i = 0, len = e.length; i < len; i ++) {
        gutil.log(gutil.colors.magenta(e[i]));
      }
    }
    // build(this);
  });

  b.on('log', function(msg) {
    gutil.log(msg);
  });

  build(b);
}

function build(bundle) {
  gutil.log('Building...');
  return bundle.bundle()
      .on('error', errorHandler)
      .pipe(fs.createWriteStream('./dist/js/main.js'));
}

// Handle the error
function errorHandler (error) {
  console.log(error.toString());
  this.emit('end');
}

gulp.task('sass', function() {
    gulp.src('./scss/**/*.scss')
        .pipe(sass({includePaths: require('node-bourbon').includePaths})).on('error', errorHandler)
        .pipe(concatCss('main.css'))
        .pipe(gulp.dest('./dist/css'));
});

gulp.task('watch', function() {
    gulp.watch('./scss/**/*.scss', ['sass']);
});

gulp.task('default', ['js', 'sass', 'watch']).on('error', errorHandler);