Persistent tag highlights when changing between buffers

I’ve put following code in my vimrc.

function ExtraHighlights()
    let list = taglist('.*')
    for item in list
        if item.kind == 's' || item.kind == 't' || item.kind == 'u' || item.kind == 'g'
            exec 'syntax keyword TagType '.item.name
        elseif item.kind == 'f'
            exec 'syntax keyword TagFunction '.item.name
        elseif item.kind == 'd' || item.kind == 'e'
            exec 'syntax keyword TagDefine '.item.name
        endif
    endfor
endfunction
nnoremap <silent> <C-h> :call ExtraHighlights()<CR>

It basically generates new syntax keywords for the current buffer based on tags collected by ctags. I pick up those keywords in my color theme. If I generate keywords for buffer A, then open another buffer B in the same window and then come back to original buffer A, the keywords are gone and I need to regenerate them.

Is there a way to make it permanent for the current vim session? I tried to call this function from BufEnter autocmd, but it’s too slow…