A limit for smilies included one after another

In comments I often found spots from bad users. There is a great number of smilies one after another (eg. :lol::lol::lol::lol::lol::lol::lol: 40times). I tried to put into config-extra something like ':lol::lol:':lol:':lol:':lol:':lol: ...etc...'' => 'icon_lol.gif' but it isnt 100% solution. So Id like to see a hack or trick that will establish a limit for number of smilies in a line (one after another). Thanx very much!