Originally Posted by irishguy28

If you fly enough to obtain/maintain status in more than one alliance, it is certainly worth considering this. It is also handy to have miles that you can spend on more than a single alliance - it gives you more options.

And you're not carrying all your eggs in one basket.

But also remember that, as Xandrios said above, any level miles earned in FB above your threshold will be automatically carried over to the next year - meaning you don't start from zero miles in the following year. This only applies, however, as long as you at least maintain your status. If you drop status level, there is no level mileage rollover.