If it is Sepia Bandensis it most likely has no more than 6 months to live, I would guess closer to 4. If it is a bigger species like S. Pharonis or S. Officinalis (I believe they live 18-24 months due to their size; not positive though) it probably has over a year to live if given the right conditions. It could be a cuttle that isn't commonly kept as well. I would find out the species before you buy it. You could try sending an email to LA asking where it was collected. That should help at least some.
They are better raised from TR eggs, although they are uncommon.