If you grow Heliamphoras in the greenhouse I would wait until they
are really growing (June or so) but if you grow them under lights you
may repot them anytime. They do NOT mind root disturbance. If you
break off all the roots just put the plant under high humidity conditions
until it has grown new roots. Most Heliamphoras die in cultivation
because they are grown to soft and are cared for too much...
Andreas