[Klaus]

Samyang AF 12mm f/2 E
Samyang AF 24mm f/1.8 FE
Sigma 35mm f/1.4 DG DN ART
Canon RF 100mm f/2.8 USM L IS macro
Canon RF 600mm f/4 USM L IS
Canon RF 400mm f/2.8 USM L IS
Fujinon 18mm f/1.4 R
Sony 14mm f/1.8 GM
Tamron 11-20mm f/2.8 Di III-A RXD
Tamron 150-500mm f/5-6.7 Di III VC VXD

I find it quite astounding that an industry on the brink releases so many new lenses

[Rover]

Wow, so hard to keep up, especially for you (and Markus). I can understand you not testing big teles though - they're probably boring due to being perfect across the frame, wide open, as their price suggests/demands anyway. Though one might have probably done well as a reference lens if you were ever in need of another.

[Klaus]

With just a single 600mm f/4 or 400mm f/2.8 per lineup, it's a little pointless to test them. As a buyer, you simply have no choice - take them or leave them.

Generally, I'm considering the mid-segment as the most meaningful place to be for us. Kit lens buyers don't care about reviews, and neither do the high-end folks.
From there on it's a matter of affordability and getting one for testing.

I'd absolutely LOVE to get my hands on the Voigtlander APO Lanthars but accepting thousands in losses just for the enjoyment of a few days is something different.

[Klaus]

Added two more to the list ...

[mst]

With just a single 600mm f/4 or 400mm f/2.8 per lineup, it's a little pointless to test them. As a buyer, you simply have no choice - take them or leave them.

Yep... plus, you can expect superior performance from any brand offering such lenses. Technically, there is also the Sigma 500/4, but given its fairly high price (and from experience: sub-average resale-value) most potential buyers would probably rather go for a earlier generation Canon or Nikon lens instead.

Within one system, it's rather a question if you need (or can afford) the latest generation lens or if portability and/or flexibility is high on your priority list. In the latter case, the x00-200/4 zoom lenses would be an option, or the DO/PF lenses.

In any case: from the investment required alone (no matter if we'd rent or buy/resell such lenses), such reviews are fairly unlikely to happen.

I'd absolutely LOVE to get my hands on the Voigtlander APO Lanthars but accepting thousands in losses just for the enjoyment of a few days is something different.

Similar feelings here. With the difference, that I'd be very tempted to get and keep one with M-mount. When the 50/2 APO Lanthar was announced, it took me some debates with myself to eventually come to the conclusion (again) that 50mm simply is not my focal length and even a stellar APO lens is unlikely to change that. But then they announced the 35/2 APO...

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Though one might have probably done well as a reference lens if you were ever in need of another.

Not really, I'm afraid. Testing long lenses comes with all kinds of challenges regarding a stable setup already, testing a fast long lens (usually with a short focus throw) adds some extra annoyances on top.

For most systems, either 50s or mild tele lenses turned out to be the reference. For Fuji it's still the XF 90, for example, for Nikon F the AF-S 105/1.4 and for Nikon Z the 50/1.8 S.

[Rover]

Yeah, I'm not insisting - I'm not in the market for any of those, the Canon 100-400 ($400 second-hand) has me covered in the "long" realm anyway. I've seen you dip the toes once - with the 200/2, and it turned out to be everything it promised (it bloody well better do, for that kind of money). Testing superteles must be boring anyway, they're so good - unless you would try evaluating a "bargain bin" supertele like a Sigma 300mm f/2.8, to see how it really stacks up to the camera brand offerings, but I guess that might not be feasible.