Once again my apologies for not taking her seriously.
I fly United, in my opinion there is a significant difference between premier and premier executive. Premier gives 25% bonus and premier executive gives 100% bonus. So if you are flying a lot next year, that is a difference of 37,500 bonus miles on the first 50,000 miles. Also upgrade situation is better with PE, and in general airlines will give better perks the higher you are in the elite chain. Similarly between PE and 1K, there is a significant difference. I would be willing to pay a little more to get to the next level. If you have some spare time, consider an extra vacation towards the end of the year (flights to Europe offer a good ratio of flight miles/airline ticket cost if one shops carefuly). If you do not have spare time, then adding an illogical itinerary in such a situation as KatW describes makes sense.
I have always advised that one should try to maximize their flight arrangements with one airline. Forget what anyone tells you about alliances, partnerships etc. Stick to one airline (and not its partners/allies) as much as possible. If you are flying internatonal, try to maximize your flights with your main carrier, take the transatlantic or transpacific route with them and then connect on shorter partner routes (rather than take the longer flight on a partner).