Hi aquarius17,

I'm sure most of us here are in at least 2 of the major alliances, if not all three.

I think it's a good idea to have membership in at least one program for each major alliance, since you are more or less sure that there will (almost always) be a program where you can bank the miles you fly. Please note however, that even though you may have membership in all alliances, it will be best to concentrate on only one of them (or two if you fly enough)

Personally I have a "major account" for each alliance, plus some additional memberships in other FFPs for banking miles flown on partners who are not part of any of these alliances.

As to what might be best for your situation, how often will you be flying between Japan and Canada? Will you be flying much elsewhere? Where are you based? In what class will you be flying most of the time?

If you do not see yourself flying on any of the skyteam partners soon, it may be a good time to redeem some of the FB miles and start building miles instead on a *A account. I understand you're considering AC Aeroplan, SQ Krisflyer and NH Mileage Club instead of your UA plan, and one of your concerns is mileage expiry. IIRC, AC and UA miles do not expire as long as you have some activity with them every so often, whereas SQ miles expire in 3 years and NH miles in 2+ years. Earning miles with NH is also not very efficient for discounted tickets (70% of flown miles I think). In the meantime, AC gets you to elite fast (please see BlondeBomber's chart for details as recommended by KiwiFlyer in your other post). With these in mind it seems that AC might be a good choice but I can't say if it's the best program out there for you. I hope though that this gives you some direction in your search.

Regards and welcome to FT!