After all, it was no longer my problem. They fired me. It was their decision. They will have to live with the consequences.

Yes, that's true. I offered them further supply of patches for critical fixes, e.g. a missing indirection in the structure of a binary blob I dissected in the database of some VPN product (the keys are arbitrary, I found out, can differ from installation to installation, and the actual key is in the structure below that and an index into another table which describes the property) - but they categorically rejected. Upon breakage, it will be hard for them to find out why. Hopefully they'll read this post.

I can't help it. But after 8 years it takes some time to get this stuff out of my head and break the ties.
"Get over it", I says to me, "other mothers also have nice daughters."

There's another point they didn't think about: my informal position. Many colleagues held me as "the guru", the last resort type of guy for tough problems: "ask him, he should know." Not that I am a guru at all, or was the key figure at the shop, but in two earlier occasions I witnessed that firing one can lead to an avalanche of other valuable people quitting, which always was a brain drain hard to cope with, and in one occasion destroyed the company.

I wish them well and hope for other changes in that shop, if any.