Legally, no. But in practice some banks refuse to accept them after 6 months. If that happens and you have the original draft, it should be straightforward to get the issuing bank to replace it. The problems arise when you want to replace a lost draft.
No, a draft doesn't expire like a cheque. Hence if a draft gets lost and you seek to replace it, the bank will usually ask you to indemnify them if the original draft ever surfaces.