I live on the coast. Sand is everywhere and it eats through chains. Oddly I actually get more mileage with less oil as it just creates grit. (Dry wax is best though). Still to suggest changing a cassette at 1500k is crazy to me. I ride 10+ hours a week, exclusively MTB with lots of shifting in sandy conditions; 3 chains and 6000k later things are going fine.
Granted if your a pro and get this stuff for free sure, keep it running like new. Bit for regular folks that’s a lot of $$$.