Yes, I saw that you like to buy and then use for many years. If you want to use a Mac and it run well for 7-10 years then, I guess, you would probably want to get 64gb as a minimum, but consider 96gb, 128gb, etc. Also, the highest SoC (M3 Max 16/40). 10 years is a hell of a long time with computers and also Lightroom Classic and other software is more and more making more use of the GPU for AI stuff. A few month ago Adobe announced that going forward more and more of the new features would require a fairly strong GPU. You are working with 45mp photos. Maybe larger later?
Unfortunately, Apple has still not fixed the Neural Engine bugs introduced in Ventura that Adobe, DxO, and Topaz has said means they cannot use it for AI stuff (DxO later came out with a temporary kludge while waiting for Apple to fix it). DxO says it was good in Monterey though. Sonoma has still not fixed the problems. The Neural Engine is a core component of Apple Silicon and major photo processing companies for a year have been saying it is broken since Ventura came out. See this for more info:
https://www.dpreview.com/forums/post/67334501
Read through this post and the links for full info about the Neural Engine bugs:
https://www.dpreview.com/forums/post/67299489
ArtIsRight talked about the Neural Engine problem in his video:
My thoughts about the new M3 Macs
For those who do not know about the Apple Silicon GPU and the similar Nvidia Cuda cores and Tensor cores which are similar to the NE then see this:
What are Apple's GPU cores?
https://www.dpreview.com/forums/post/67117906
Neural Engine - Nvidia CUDA Cores vs. Tensor Cores: What's the Difference?
https://www.dpreview.com/forums/post/67118578
Personally, I do not buy with the expectation that I will use for 10 years. Having said that, I do have 4 old Windows laptops (oldest is over 11 years old) that still run fine with Windows 10 and LrC works pretty well on them (my largest photos are 20mp though) -- all have an SSD, one has 32gb RAM, three have 8gb RAM.
With Macs though I prefer to get what I think will work fine for 2-3 years and then see how things look after that time. My current 16" M2 Pro 12/19 MBP 32gb/1tb may very well be going strong and working well a decade from now, but probably when the M4 comes out I will likely be tempted to buy a new one.

The way Apple has been releasing Apple Silicon with a new version about every year I suspect the M4 will be sometime next year.