I had some misoto rose radish seeds from 2011 that sprouted beautifully this fall but other seeds from the same company and year are dead. I admit they were in supposed climate controlled storage for 3 months while we built our house. I was surprised the radishes still had life. Just wondering if I store them in cool location can they generally be used a second year?

I tested the seeds by dampening a paper towel and placing 10 seeds on it, then closing up in zip bag. If 6 sprouted then I had a 60% sprout rate. The radish were 80%. All the others were zero.

I find that most seeds are good for at least two years from purchase dates.
How long the seeds are viable depends on the particular plant, and how they are stored.
Some seeds are more viable after dry storage, and some lose viability on storage.

Your method of testing for seed viability is a good one.

If I am using older seed---then I often sow them thicker to compensate for lower germination rates.

There is a "sticky" thread on seed longevity right here at the top of the thread list that has links to a couple of sites with good information on the subject.

The thread "Seed Longevity Chart" in Seeds forum