Do these brake discs need replacing

[mawallace]

Took my car for an MOT at the local dealer. they made a number of advisories, one of which was my rear discs which were 'showing signs of corrosion'.

I asked for proof and where given these pictures. They said they were 85% worn.

There's no sign of juddering.

The car has done 59,000 miles - they are the original.

I was wondering how often they should be changed.

Thoughts please?

[mawallace]

Thanks for the replies. The car is 4 years old,done 60000 miles.

I now do approx 16000 miles a year