Originally Posted by
pinniped
A short EI segment probably isn't worth the J miles. I love EI for the ability to use a fairly small number of Avios to get the family to/from Europe in Y (13,000 per person off-peak from Chicago with almost no fees) but it's always seemed like a poor value for J.
The AC options would be attractive to me because I enjoy visiting Toronto in general. Always a fun place to spend a day if your schedule permits a long connection like that.
There is some flexibility (within reason), so we may be able to swing a day in Toronto. AF could be interesting too as LAX-CDG is on the A380 (which I've yet to fly), but I'm not sure how I feel about angle-flat seats. Various video reviews seem to be fine with it though and if I'm not going to be getting much sleep anyway...
Anyway, it sounds like there isn't a hard and fast rule for how long one should fly before being able to justify upgrading. For instance, going through Toronto might very well necessitate J even on the relatively short 4-5 hour transcon leg considering that one may need to be awake the entire day afterward before the next leg.