Unpopular opinion: Island Vanilla Dunes is better than Althair
You can look through my posting history...I am a HUGE Parfums de Marly fan. I own full bottles of Carlisle, Layton, and Greenley. I have bought their 7 cologne sampler pack and love almost all of those. I fully intend on buying Percival and Haltane in the next couple months. I'd consider either Oajan or Herod as well.
That said, I was really excited to try Althair because of the descriptions and reviews. When I got my hands on the sample, I liked parts of it but there was a harsh sharp wood tone that I just didn't like and couldn't get past. So I gave the rest of my sample to my 13 year old son who is building a collection, and he LOVED it. But unless it's some very special occasion, neither he, nor I on his behalf, would pay that much for something for a 7th grader so I looked into some dupes and got him Khadlaj Island Vanilla Dunes for like $35. But I love it too. It has all the parts that I did love in the Althair (and smells REALLY close to the original), but to me the wood tone is mellowed down and doesn't have the sharp quality that was off putting to me. I think it's fantastic. I've been stealing sprays from him. It's very long-lasting too.
This has got to be the only time I have thought a dupe smelled better than the original...especially for someone for whom PDM is so beloved. It's like they made it 95% identical to Althair, and the 5% difference was exactly what I didn't like about the OG.