My milestones were $40k, $45k and $50k to earn 50k/75k/125k bonus RDM's.
I am going to hit the $40k in a week or so and then a Thanksgiving ski trip in Europe will pull me over the $45k mark, so I should get 125k extra miles. Got lucky as my flight home from Switzerland is on November 29th.
I have barely been using GPU and CPU this year, and together with my husband who will hit 1K I think we have 15 GPU's for us 2. Only time I ever use them is when I am on a D class fare or higher and can sneak into the shrinking Global First cabins. Great perk as the privacy in GF seats is a nice way to travel, although I guess Polaris will still retain a bit of that privacy if not such a large space.
I really only bought one $2k ticket to go see a play my sister is putting on to make sure i get past the $45K spend - don't really need extra miles!