OK, current real-world example here, and why I have the best wife in the world (also, as a sidebar, addresses the age-old seat swapping with strangers discussion):

We're flying to NYC next week, but we're originating from different cities (I'm flying in from MSP from work, she's coming up from home in GPT). We're both returning on the same 2 flights (connect in MEM) back to GPT. So, we're on different itins. My Plat UG % on NWA this year has been well over 90%, so I'm pretty confident I'll be getting upgraded. My wife has no status.

I've selected our seats on the 2 return segments so that we're next to each other in aisle and middle seats on both segments. I've made sure that *I* have the middle seats. Objective: Presuming I get the UG and she doesn't, we forfeit my middle seat. Then, I give my wife the UG, and I slide over to her aisle seat, both flights. (Of course if I miss my UG we're still sitting together.)

My wife has indicated that if this happens on both segments, she'll take me up on the UG for the longer LGA-MEM segment, but says she'll let me have the UG no problem on the short MEM-GPT. She says that's only fair. I love my wife. Oh, and we wouldn't even CONSIDER declining at least one UG...it's more important for at least one of us to have comfort in FC, and we can survive sitting apart for a few hours (hell, we survive being apart every week when I leave town for work!).

The side benefit is that thru this judicious planning, I don't have to ask any strangers to switch seats for us to sit together. (Of course this goes right out the window if there's an aircraft change or other irreg ops, but what can ya do in that case.)

Oh, and one more thing: If I do catch the UG and she doesn't, I still do plan to ask the GA at each flight if she can also score a companion UG even though we're on separate itins, since I'm NWA WP Plat. I've had better than 50% success with this request in the past, depending on availability that day.