Heat sinking op-amps - any audio improvements?

Nope.

Great little op amps though, shame the 5535s didn’t last. I think Benchmark wrote a paper on them, pointing out that they are great if you deal with the power supply properly. That may be worth investigating. We used them a lot with +- 15V supplies and had tiny local bypass caps for the power supplies. 1-4.7uF or something

I’m debating trying some on some NE5532’s. Worth the effort?

Why not? It's an inexpensive tweak and can easily reverted.

@imhififan 

Why not? It's an inexpensive tweak and can easily reverted.

Most definitely. I didn't reply, because I had already decided in my mind that I was going to do a little experimenting anyways. IMO, it's the perfect winter project. I have some NE5532's that have been powered up for around 21 years 24-7-365. I applaud that chip, and the design of the piece of equipment they are installed in. I know it sounds crazy, but maybe keeping them even a little bit cooler might be beneficial.     

I know it sounds crazy, but maybe keeping them even a little bit cooler might be beneficial.     

Crazy? Not really.

Thermal Design Basics - Analog Devices