It's better if you don't believe me as I don't know enough about this. My worst experience was with a 4GB of memory computer and it took months. In a 16GB computer I never did the IBD, just copied from the another to it, but even that computer was struggling to keep up with the chain, so eventually I had to shut the node down. The segwit blocksize increase was very bad for Bitcoin.

Are you storing only the blocks on an external SSD or the chainstate too? I think if you keep the chainstate closer put the blocks away that will be better. Probably Bitcoin Core doesn't even support that. Anyway, I'll just shut up.