Vim：一段时间后自动退出插入模式

" set 'updatetime' to 15 seconds when in insert mode
au InsertEnter * let updaterestore = &updatetime | set updatetime=15000
au InsertLeave * let &updatetime = updaterestore

" automatically leave insert mode after 'updatetime' milliseconds of inaction
au CursorHoldI * stopinsert

我在MacVim中使用此代码段,但它不起作用.当我进入插入模式,我什么都不做,
Vim在15秒后离开插入模式.但是,如果我按Enter键或退格键,或者我进入插入模式
使用o / O,然后Vim立即离开插入模式,此时,即使我使用i进入插入模式
Vim立即回到普通模式.

我在Mac OS X 10.8.5上使用Homebrew安装了MacVim

任何想法为什么这不起作用？

编辑：这是我的MacVim版本,包含所有标志：

VIM - Vi IMproved 7.4 (2013 Aug 10,compiled Sep 29 2013 02:17:27)
MacOS X (unix) version
Included patches: 1-22
Compiled by Homebrew
Huge version with MacVim GUI.  Features included (+) or not (-):
+acl             +file_in_path    +mouse_sgr       +tag_binary
+arabic          +find_in_path    -mouse_sysmouse  +tag_old_static
+autocmd         +float           +mouse_urxvt     -tag_any_white
+balloon_eval    +folding         +mouse_xterm     +tcl
+browse          -footer          +multi_byte      +terminfo
++builtin_terms  +fork()          +multi_lang      +termresponse
+byte_offset     +fullscreen      -mzscheme        +textobjects
+cindent         -gettext         +netbeans_intg   +title
+clientserver    -hangul_input    +odbeditor       +toolbar
+clipboard       +iconv           +path_extra      +transparency
+cmdline_compl   +insert_expand   +perl            +user_commands
+cmdline_hist    +jumplist        +persistent_undo +vertsplit
+cmdline_info    +keymap          +postscript      +virtualedit
+comments        +langmap         +printer         +visual
+conceal         +libcall         +profile         +visualextra
+cryptv          +linebreak       +python          +viminfo
+cscope          +lispindent      -python3         +vreplace
+cursorbind      +listcmds        +quickfix        +wildignore
+cursorshape     +localmap        +reltime         +wildmenu
+dialog_con_gui  -lua             +rightleft       +windows
+diff            +menu            +ruby            +writebackup
+digraphs        +mksession       +scrollbind      -X11
+dnd             +modify_fname    +signs           -xfontset
-ebcdic          +mouse           +smartindent     +xim
+emacs_tags      +mouseshape      -sniff           -xsmp
+eval            +mouse_dec       +startuptime     -xterm_clipboard
+ex_extra        -mouse_gpm       +statusline      -xterm_save
+extra_search    -mouse_jsbterm   -sun_workshop    -xpm
+farsi           +mouse_netterm   +syntax          
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
      user exrc file: "$HOME/.exrc"
  system gvimrc file: "$VIM/gvimrc"
    user gvimrc file: "$HOME/.gvimrc"
2nd user gvimrc file: "~/.vim/gvimrc"
    system menu file: "$VIMRUNTIME/menu.vim"
  fall-back for $VIM: "/Applications/MacVim.app/Contents/Resources/vim"
Compilation: cc -c -I. -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_MACVIM -Wall -Wno-unknown-pragmas -pipe  -DMACOS_X_UNIX -no-cpp-precomp  -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1     -I/System/Library/Frameworks/Tcl.framework/Headers  -D_REENTRANT=1  -D_THREAD_SAFE=1  -D_DARWIN_C_SOURCE=1  
Linking: cc   -L.   -L.    -L/usr/local/lib -o Vim -framework Cocoa -framework Carbon       -lncurses -liconv -framework Cocoa   -fstack-protector -L/usr/local/lib  -L/System/Library/Perl/5.12/darwin-thread-multi-2level/CORE -lperl -lm -lutil -lc -framework Python  -F/System/Library/Frameworks -framework Tcl -framework CoreFoundation -framework Ruby