Your parents can apply for a B-2 independently of your immigration status, but we would review you and your parents’ timelines and goals to help with an approvable process.
Your parents can apply for a visitors visa at any time. Your conditional or unconditional permanent residency will have no bearing on the granting of the parents B-2 visa. That is, the fact that you have permanent residency status will not be a basis for the parents to visit and stay in the U.S.