Thanks for the replies guys...

Most of the meta descriptions are unique but some are duplicate so I'll go through and make sure each is 100% unique. Thanks crankydave, that's an easy one to fix but I doubt it will solve the prob completely.

I found this tool - Supplemental Index Ratio Calculator which is pretty handy.

It's actually very interesting. I was testing out a few competitor sites... eg if you run it for

Used Cars - New Cars - Search New & Used Cars For Sale - carsales.com.au you get

Google has a total of 24700 pages indexed from Used Cars - New Cars - Search New & Used Cars For Sale - carsales.com.au
1690 are in the main index
23010 are in the supplemental index

This means an amazing 93% of carsale's pages are in the SI

and then run for Used Cars & New Cars for Sale | Car Sales | Car Reviews | drive.com.au (a direct competitor)


Google has a total of 136000 pages indexed from Used Cars & New Cars for Sale | Car Sales | Car Reviews | drive.com.au
70300 are in the main index
65700 are in the supplemental index

Which is only 48%

However, the fact is that CarSales get's heaps more traffic than Drive (over twice as much I think) despite having a fraction of the amount of pages Drive has in the main index.

So whilst anyone would want as many pages as poss in the main index, it doesn't seem to be the be all and end all (disclaimer: of course both these websites will attract traffic from lots of other sources other than organic searches)

Anyway, I'm digressing - anyone got any comments regarding my original question - about whether adding fresh content will further cause SI angst and if you do, what's the best way to do this and avoid these issues?

Thanks again