Ive wondered why there wasn’t a D1 monetization thread... Judging by the answers here, upgrades don’t appear to be offered that often.

I’ve flown LAX-CDG rt 4 times this past year, actually more but for data point I’m not including flights where I booked D1. I was only offered D1 upgrade on one leg (CDG-LAX) and it was approximately 3 months before the flight. I took the offer begrudgingly @ $990

Ticket was KLM paid coach v fare. (20k Amex MR promo) i then paid for upgrade to c+ with Delta, it changed the ticket stock to delta. upgrade was offered around 30 days thereafter, which was 90 days before flight.