With the oldest members of the millennial generation now approaching 40 – the Pew Research Center defines millennials as born between 1981 and 1996 – many have been working hard in highly-paid jobs for several years. They now have seemingly endless disposable income to spend on life’s finer things.These high net worth millennials may be catching up with their Gen X and Baby Boomer peers in terms of wealth, but they have very different views on what they consider to be ‘luxury.’ In the travel industry, this means that businesses must adapt their offerings to be in with a chance of turning these wealthy youngsters into loyal customers. With millennials typically more likely to spend their money on experiences rather than things (according to research by JP Morgan), this is a group that vacation marketers need to understand to enjoy a slice of their wealth. With that in mind, here are two things that will define the next generation of luxury travel.What does high net worth millennials want from their travel?Meaningful eco-credentialsEco-conscious travel is not going anywhere, with blogs such as Lux Digital reporting that younger affluent generations are now highly conscious of the environment and the impact of their purchases. This means that luxury brands must now be able to offer a truly eco-friendly option while still delivering five-star service. Many millennial clients will not be appeased by small concessions to the environment, demanding that whichever company they travel with has a real commitment to the planet that runs through everything they do.Think boutique hotels which source all their ingredients from sustainable sources, and employ local businesses for design and construction work wherever possible. Airlines that don’t just offer carbon offset options but who show their commitment to the environment through donating to eco-charities, investing in newer aircraft to reduce their fuel consumption. And cutting unnecessary inflight magazines.For those looking to charter a yacht, this could mean ensuring that the vessel they choose is dedicated to reducing plastic waste – many superyacht charters now have water filter systems onboard instead of distributing plastic bottles to guests, responding to this heightened guest awareness. High net worth millennials who wish to buy their own yacht to explore the world will look to hybrid superyacht construction yards rather than those that only offer classic motor yachts, aiming to reduce the emissions they will put out while they travel.The top brands for millennials when it comes to eco-friendly luxury travel include the Six Senses hotel group, which commits fully to sustainability with its aim to be completely free of plastic by the year 2022 and an organic garden in each hotel; and Nobiskrug, which crafts high-tech sustainable luxury yachts built to last for generations to come.Personality-based, all-encompassing serviceOf course, luxury has always been synonymous with amazing service, but high net worth millennials expect a different approach. Whereas traditional luxury lavishes the customer with attention, we now see demand for different styles of service depending on the personality of the individual.A report by Amadeus Travel Intelligence points to the fact that while more extroverted people may enjoy interacting with different members of a hotel, villa or yacht’s hospitality team and learning about the available experiences in person, more introverted people may prefer to have a respectful and minimalist service, with all this information clearly laid out in their room for them to digest in private. This is something that should be available at the high end of luxury travel.The top brands for millennials craving this personalized service include Rocco Forte Hotels, which teaches its service team about the different personality types so that they can better read them; and luxury travel agent Ode to Joy, which records audio files where its team talk about the experiences they can offer and sends them to certain clients, recognizing that not everyone wants to endure long phone calls to plan their holiday.High net worth millennials are revolutionizing the world of luxury travel, and brands would be wise to cater to their desires in order to benefit from this new generation of wealth.