Did you know that vim has tabs built in?

vim -p Theme.c Timer.c World.c

You’ll get this:

To switch between tabs use:

gT
gt

Or, for the inclined, add this to your .vimrc:

set tabpagemax=128
map <C-h> gT
map <C-l> gt

And now you can switch between 128 open tabs with Ctrl + H and Ctrl + L.