Use mappings.
To activate highlight:
:nnoremap <leader>1 :match Search '\%>80v.\+'<CR>
To deactivate it:
:nnoremap <leader>2 :match none<CR>
UPDATE to use same key/key combination to toggle highlight:
let s:activatedh = 0
function! ToggleH()
if s:activatedh == 0
let s:activatedh = 1
match Search '\%>80v.\+'
else
let s:activatedh = 0
match none
endif
endfunction
nnoremap <leader>1 :call ToggleH()<CR>