Next general M+S question: When to upgrade with points, and when to upgrade with a voucher?
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• Obviously, you want to use the voucher when it would cost a lot of points to upgrade. Sydney to San Salvador, here I come!

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Beyond that, I think points are strictly more flexible (unless they are about to expire), so you should always use the voucher?
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• Vouchers expire after one year, points expire after three
• I believe the vouchers can only be used on TK flights (what about codeshares, whether TK code on *A metal or vice-versa?) whereas points can be used on *A
• Vouchers can only be used for you and your "family membership" members, whereas points can be used to upgrade anyone(?) flying TK (again, not sure about codeshares)
• Points can be used to upgrade one leg (e.g. if upgrades on the other leg weren't available) whereas that would be poor use of a voucher
• Points can be turned into Amazon vouchers, etc

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Any other considerations?
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• Is availability always the same for both? I think I read that you can upgrade iff there's J availability for both/all legs, regardless of whether you're using points or a voucher. I'm not sure if e.g. IST-SIN-MEL counts as one leg or two in this context.
• Regardless of which way you upgrade, you get reward+status points credited as per your economy ticket(?)
• If you are upgrading both yourself and someone in your family membership, and want to do one upgrade with points and the other with a voucher, is there any reason to use the voucher for yourself and the points for the family member, or vice-versa? If the point above is true then I can't think of one. I guess you use the voucher first in case there's only J availability for one leg once you've done so.
• Anything I've missed?

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Thanks