Short version: If you offer users a discount for paying yearly instead of monthly, why not generalize that and give them a slider to choose how often they'll pay. Every 2 months, every 6 months, every year, every 2 years, every 5 years, ... You can even let them pay once for a lifetime subscription. We made a little demo of it and give the equations for computing the discounts perfectly fairly for any payment frequency.

It's pretty great (if your users happen to be huge nerds)!

I think this gives users too many decisions to make. Too much choice can be daunting.

I did think it sounded too crazy to actually do, but I really like the way it turned out (did you try our demo slider?). And it is just a single slider, so not as bad as multiple decisions, exactly. Admittedly it's harder than "monthly vs yearly" though.

In any case, I won't be surprised if you're right and it only makes sense if your users are nerds who will like it for it's own sake. :)

But there's a slider!

Slightly more seriously: for us, the premium plans are directed more to the hardcore users who are already committed and love the service, so more choice is maybe less daunting?