My threshold for adding MRs would be if I were about 10k to 15k short.
I did 3 transcon cheap MRs during AADER as I was pretty sure I wouldn't make 100k BIS this year. However, since I'm going SFO-NBO soon (~21k EQM) it looks like I will end up with 115k total, so one of those MRs was a waste... oh well, my crystal ball was a bit cloudy. Most likely I have no chance to get to 125k by year end to score 2 more eVIPs, unfortunately.