High Mileage Lease (15K or 20K) BMW loaners

I see a lot of great bmw loaner leases on here with mostly 24/10. Is there a significant downside with other lease timeframes and mileages?

I put about 15-20k miles per year. I would like a 24/15, 24/20, or 36/15 lease.

Can these leases be leasehackr worthy or is there something magical with the 24/10 type?

Thanks for your inputs.