It's theoretically possible to upgrade all long trips as a 1K. There's the 2CR1s, 6 SWUs to start. Plus 2 CR1s per quarter, plus 40 500-mile certs for 100K miles, plus the 200K miles (100K miles plus 100% bonus).

What helps: 1) short trips with no upgrades - saves them for long hauls, 2) TED which has no upgrades, 3) really long overseas trips where a SWU goes a long way.

Then you can save them for the following year.