Actually, 10,000 seconds sounds exactly right for a cold breeder -- did your efficient breeder have time to heat up to 64,000 heat? The other problem is probably that you got the cell out of NEI or Creative: they come pre-cooked out of there; try crafting the depleted cells and see if it makes a difference.
Edit: Also, be aware the planner only shows you that the heating cells in the bottom-right corner are actually a stack of 64 heating cells if you hover over it -- this may have some relation to your problem.
yes, this sounds like it's the right direction. I'll put in a stack of these heating cells. How can I check the heating of the breeder - is there a way in vanilla ic2? How do I heat up the breeder?
Heating Cells will heat up the breeder.
