Just been into the garage to check on this for my Passat. VW UK recommends replacement at 80,000 miles or 4 years , which ever comes first. I was advised the cost would be around £350.

same as my old Passat then. I left it for nearly 6 years as car had only done 70K miles and belt went and trashed the head. VW wanted £2K to do it, the local independant £1200, so I bought a Haynes book of lies and the odd special tool and did it myself for £350. Anyone else needs their head reconditioned I can highly recommend Engine-Express in Bury. Collected head, full recon, all valves and a light skim then couriered back with all gaskets and a full set of new stretch bolts...all for less than £300. I couldn't have bought the valves for that!