AFAIK losses can be carried forward indefinately.
Just remember to deduct expenses both buying and selling and you can't make use of the mulpitlier to increase losses.
Capital losses can be carried forward indefinitely and set against subsequent capital gains. Ideally you should have made a CGT return to record the losses althogh I inadvertently failed to do so in the past and Revenue accepted my calculations when I offset such losses and provided detailed calculations.
This (complex) thread might be of use to you in attempting to calculate your losses: