I have a $2400 voucher from the TYP pre-devaluation rush. It was an intl non-refundable ticket that I changed into a domestic flight - the $2400 is what was left after that. The voucher has "Treat as Type B Voucher" note on it, and explicitly states that it can be used only for UA/UAX and not codeshares.

However, I don't do much domestic flying. I have a European trip coming up, but United doesn't fly their metal from BOS direct to Europe, and going via ORD or IAD is a hassle and a waste of time (easily 4+ hours extra each way). So, I started thinking along these lines:

Option 1: buy a refundable ticket for the full amount, then change it to a codeshare I want.

Option 2: (if refundable ticket is a problem) buy a non-refundable ticket for the full amount, make the change, eating up the change fee.

Option 3: Take no risk, pay cash for this trip, and gradually use the voucher for whatever flights I make that make sense with UA hub layovers, extending voucher validity by buying cheap throwaway tickets whenever needed.

Note: for that Euro trip, I need tickets for two or may be three people, not just myself.