Originally Posted by flysurfer
Since the OP stated it's all in coach, I guess we should stick to this assumption and not cause more confusion than necessary
Okay so I try to give a simple advice
I'd credit the miles to an other program then M&M if you just fly Y. I'd only use M&M if you have a lot of C and F segments or if you'll fly a lot on LH metal and therefore what to get LH status.
UA is quite okay and with your routing you should earn enough miles to get 2P. And as
andyZRH mentioned MP miles don't expire as long as there is any activity on your account every three years which is quite easy to be done. If you want to get status and if you'll fly some more segments this year, you could also try AC aeroplan. *G can be done with just 35k miles.