When were the best tube amps made?

Tomorrow.

I'd still go with a properly maintained 240.

Having both vintage and new tube components, I prefer the older stuff - think Marantz 8B, Fisher 800c, Citation I and II, heck even my original Sansui 1000x is highly regarded in a sea of vintage and new solid state and tubes. The older stuff often benefits from simpler designs and less complexity in the signal path. Of course modern technology is more advanced, but modern tubes sound more like solid state to my ears. Why would I want printed boards in a tube component? All that said, I’m on the waiting list for a Decware triode amp. Gotta see for myself what all the hype is about. 

Most individuals today only receive demonstrations from a very modern design for a Tube Amp'.

The Companies were becoming more 'Corporate Like' the Bean Counters were taken advice from Techies who had not respect for tradition.

Resulting in designs that were enforced to change Topology and Schematics were designed to omit Transformers from the Circuits. Streamlining the component count and casing dimensions took precedent, over overall performance.

If a Amp' with circuits from the period of Halcyon, is discovered and breathed on with a sympathetic approach, using the accuracy of modern components to interface with the Olden World irreplaceable components, now one is 'cooking on gas'.

Barn finds are still big business, as the few in the know, charge substantial amounts to allow another to share in the secret.