There are many opinions on this forum (and I'm sure they will pipe up !) But I think Alfa recommended is 5 years or 72k miles. Others on here recommend lower numbers. My latest v6 Spider 2001 with 30k miles has had two changes. The most recent in 2012, so one of the previous owners took it over the 5 years, I recon I'm ok for another 3 and a bit years
I had a similar story to Mitch, but with a mere 1.6CVH Escort MkIII. Was a few thousand away from belt service recommended 60k and watched an episode of Top Gear (when it was actually a motoring show!) they said get them done at 40k; I thought better book that in then. Booked it in, and the belt went 3 days before it was going in to be done! Grrr
Mines done 47k with one belt change about 10k miles ago in early 2008. no record of a water pump change and the spark plugs need changing as well so I'm psyching myself up to changing the belt, pump,plugs etc all at once. I know its not a job for the faint hearted but when I bought the car a promised myself I would do all the work rather than pay someone else. Ive got some special tools from Totally Alfa and Ill try to post a tutorial once (if!) I manage to do it.
Go for it, i have done 2 v6 belt changes, the water pump is the worst bit to do, don't forget to loosen all four cam pulleys once everything else is locked up, i have a step by step guide for V6 belt change in my workshop if it's not to dirty i could do you a copy. Before you send the whole day and get up to your elows in Alfa V6 i would check out Totally Alfas website as they quite often have a good deal on belt changes.
another one here with a snap at 71k miles, luckily the previous owner had to foot the bill, although the chumps only did the tensioner and belt, so I had to do the idlers, therefore the job all over again, and the water pump while I was there.
I ran the belt to 72,000 miles on my 12v and it came off with hardly any wear on it. But the beast was doing the mileage though, so that belt was only aboot 3 years old and mostly on motorways.
The tensioner, on the other hand, almost did two Tours of Duty... running up to 120,000 miles when I removed it.. and that was well "racey". It may have survived to 144k but I don't think my nerves would have!