That's your call. Do you want to release them? If they're well and healthy, and you feel as though they could lead "fuller" lives outside, then it might be an idea, you've potentially done them a service by fattening them up at a time of year when others could be hibernating. On the other hand they might be disadvantaged if you've prevented them from having a winter cooling period (I'm not too familiar with this species so I wouldn't be able to tell you whether this species needs one), or by making them comfortable in the presence of much larger animals. When I was a kid I caught a male wall lizard in southern France. I kept him for a year, and even though he was already an adult he grew about 50% in length in captivity and became much more heavily built, despite this he had also become more tame around humans. After releasing him (because we figured that in captivity we wouldn't be able to breed him) at the same location in southern France, I am unsure whether his large size and increased muscularity made him more competitive than the other lizards, or if this, combined with his more outgoing disposition led to a fate as food for another animal, roadkill, or the victim of a passerby's foot.
The ethics of taking a wild animal into captivity are complicated, though often minor, it may have unforeseen affects on the individuals and the local populations.