BFG A/T's - When are they "Worn"?

When would you consider a set of BFG A/T's to be "Worn"and in need of replacement?

Having never owned my own landy before I assume that 1.5mm may be a little below what is required

Got a quote for 4 x 235/85R16's at £388.00 all in including fitting/balancing/valves etc. Anybody seen a better price?

Lastly are the mud-terrains very noisy on-road? I tend to use the my vehicle off-road about 50% of the time but do take it away with us camping etc. which necessitates the odd road trip. Are they excessively noisy compared to the A/T's on it at the moment?

Thanks.

I have mud terrains on my 90 and I find it fine, it is noisey, if you coast (so you don't have the engine noise) there is a fairly noisey humming sound.

You could add some sound proofing if its going to cause you great grief.