OP, you're a classic example of a customer who will find greater value / rewards in being disloyal, and shopping around for best fares. With one or two TPAC crossings per year and < 20k miles banked in 2.5 years, it might be costing you more to remain UA-loyal than to just fly whomever is cheapest.
If the difference between the cheapest possible ticket and a United ticket is, say, $100, and you spend that $100 ten times over, you have spent an aggregate $1,000 to earn miles that might be redeemable for a TPAC ticket that probably would cost you less than $1,000. Do the math. Loyalty at your level can cost you, not reward you.
At this rate it might take you 5 or 6 more years to rack up enough miles for one free TPAC ticket anyway, and there's no guarantee UA won't move the goal posts between now and then anyway -- now that dynamic pricing is coming in you literally have no idea of the real redemption value of your MP balance.