Clearing out the chaff can have a beneficial effect in allowing one to re-evaluate past practices and develop new ones.Thank you for your response. I do see the benefit of getting rid of KW where there have been no, or almost no, impressions in the last few years, they were a gamble which didn't come off, deleting them tidies up the account. I started with about 580 kw, after deleting the zero impressions ones and pausing those with low quality scores (quite a few) I now have 140 enabled kw.
Even more important when the budget is limited!