Should I stop these alstroemerias growing?

Berkley

I always overwinter my potted alstroemerias. I pull the stems left in the Autumn and store them in a cold but light garage. But this year they have responded to the usual routine by producing numerous stems which are already up to twelve inches tall. Should I remove them now or leave them until early Spring?

Posy

I'm not sure why you remove them. I put mine in an unheated greenhouse and they flower all winter, in a modest way. Pulling the stems encourages new growth, I believe. Outside, they become dormant and disappear for the winter.

Fairygirl

I's be inclined to leave them rather than cutting back if it's new growth. It has been a much milder winter in many places [winter hasn't even started here where I am] and they've probably just responded to the conditions and therefore earlier. 
You might want to consider getting them hardened off and outdoors, rather than keeping them inside, and that will slow them down a bit, and prevent them getting too leggy.