Npm Change $Path Isn't Perminent, Only per Terminal?

Recently I have changed OS to Linux Ubuntu for development. I have installed Node.js & NPM to use with Yeoman, after installing NPM I followed the official documentation on permissions Docs. As my displayed path was just /usr i followed Option 2. Everything went well and I proceeded to install Yeoman, Bower & Grunt and everything was fine. However Yeoman, Bower & Grunt do not work in another terminal window. each time I open a terminal I must follow Option 2 again before I can commence usage. Why isn’t my $PATH staying updated? What am I doing wrong?

Also, while im asking. NPM is running like a snail while installing, it took me probably around 5 hours to install Yeoman, Bower, Grunt & Webapp-gen and it took around a hour to make a new project yo webapp last night. Anyone know why this may be? it's still running like a snail today - Internet & hardware usage are all normal and in the green, git, composer, bower etc are all running at normal speed. Its just NPM.

makka@ML:~$ node --version && npm --version && git --version && yo --version && bower --version && grunt --version
v5.4.1
3.5.3
git version 2.5.0
yo: command not found
makka@ML:~$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
makka@ML:~$ cd //usr/local && ls -la
total 40
drwxr-xr-x 10 root root 4096 Oct 21 16:49 .
drwxr-xr-x 12 root root 4096 Jan 18 00:14 ..
drwxr-xr-x  2 root root 4096 Jan 18 01:22 bin
drwxr-xr-x  2 root root 4096 Oct 21 16:49 etc
drwxr-xr-x  2 root root 4096 Oct 21 16:49 games
drwxr-xr-x  2 root root 4096 Oct 21 16:49 include
drwxr-xr-x  5 root root 4096 Oct 21 17:00 lib
lrwxrwxrwx  1 root root    9 Jan 17 20:27 man -> share/man
drwxr-xr-x  2 root root 4096 Oct 21 16:49 sbin
drwxr-xr-x  8 root root 4096 Oct 21 17:00 share
drwxr-xr-x  2 root root 4096 Oct 21 16:49 src
makka@ML://usr/local$ ls -la ~/
total 188
drwxr-xr-x  23 makka makka  4096 Jan 18 16:19 .
drwxr-xr-x   3 root  root   4096 Jan 17 20:31 ..
drwx------   3 makka makka  4096 Jan 18 02:57 .adobe
-rw-------   1 makka makka  3012 Jan 18 16:46 .bash_history
-rw-r--r--   1 makka makka   220 Jan 17 20:31 .bash_logout
-rw-rw-r--   1 makka makka    43 Jan 18 05:01 .bash_profile
-rw-r--r--   1 makka makka  3771 Jan 17 20:31 .bashrc
drwx------  22 makka makka  4096 Jan 18 03:59 .cache
drwxrwxr-x   2 makka makka  4096 Jan 18 01:20 .composer
drwx------  24 makka makka  4096 Jan 18 05:46 .config
drwxr-xr-x   3 makka makka  4096 Jan 18 05:48 Desktop
-rw-r--r--   1 makka makka    25 Jan 17 20:56 .dmrc
drwxr-xr-x   2 makka makka  4096 Jan 17 20:56 Documents
drwxr-xr-x   4 makka makka  4096 Jan 18 02:16 Downloads
-rw-r--r--   1 makka makka  8980 Jan 17 20:31 examples.desktop
drwx------   3 makka makka  4096 Jan 18 16:19 .gconf
drwx------   3 makka makka  4096 Jan 18 00:01 .gnome
-rw-------   1 makka makka   604 Jan 18 16:19 .ICEauthority
drwx------   3 makka makka  4096 Jan 17 20:56 .local
drwx------   3 makka makka  4096 Jan 18 02:57 .macromedia
drwx------   4 makka makka  4096 Jan 17 23:31 .mozilla
drwxr-xr-x   2 makka makka  4096 Jan 17 20:56 Music
drwxrwxr-x   3 makka makka  4096 Jan 18 02:58 .node-gyp
-rw-rw-r--   1 makka makka    23 Jan 18 04:55 .node_repl_history
drwxr-xr-x 823 makka makka 36864 Jan 18 02:58 .npm
drwxrwxr-x   5 makka makka  4096 Jan 18 00:48 .npm-global
-rw-------   1 makka makka    21 Jan 18 05:19 .npmrc
drwxr-xr-x   2 makka makka  4096 Jan 17 20:56 Pictures
drwx------   3 makka makka  4096 Jan 18 00:01 .pki
-rw-r--r--   1 makka makka   675 Jan 17 20:31 .profile
drwxr-xr-x   2 makka makka  4096 Jan 17 20:56 Public
-rw-r--r--   1 makka makka     0 Jan 17 20:57 .sudo_as_admin_successful
drwxr-xr-x   2 makka makka  4096 Jan 17 20:56 Templates
drwxr-xr-x   2 makka makka  4096 Jan 17 20:56 Videos
-rw-------   1 makka makka    47 Jan 18 16:19 .Xauthority
-rw-------   1 makka makka  1576 Jan 18 16:19 .xsession-errors
-rw-------   1 makka makka  2804 Jan 18 16:16 .xsession-errors.old
makka@ML://usr/local$ npm config set prefix '~/.npm-global'
makka@ML://usr/local$ export PATH=~/.npm-global/bin:$PATH
makka@ML://usr/local$ source ~/.profile
makka@ML://usr/local$ node --version && npm --version && git --version && yo --version && bower --version && grunt --version
v5.4.1
3.5.3
git version 2.5.0
1.6.0
1.7.2
grunt-cli v0.1.13
makka@ML://usr/local$ echo $PATH
/home/makka/.npm-global/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games

Many thanks, Regards, Matt