Any real strategy for tracking low volume keywords?

Or do you just have to use your gut?

[limitup]

Is there any real strategy for tracking/culling low volume keywords? We track every keyword for conversions, ROI, etc. but we have 1000s of "long tail" keywords with very low volume and for many of them it would take 6 months to build up enough data to make an accurate ROI-based decision. Do you just have to use your gut feeling on these keywords when deciding if you want to keep them or not?

[poster_boy]

We group and monitor long-tail keywords based on a number of similar qualities - product line, match type, similar words, format, language, etc.

Not so easy to group in all our cases, but it helps in the vast majority of cases.