Can a parent wait too long before bringing legal action under the Hague Convention for the return of children abducted to Israel?

Yes. Technically speaking a parent has one year from the time of the alleged wrongful removal or retention until the plea for their return is actually filed at the Israeli Family Court - that is to enjoy the presumption of a quick return under the Convention. After that time, the court has discretion not to order a return if the children are shown to be settled into life in Israel… and after one year it is highly likely that they will have done so, unless they are very young. In practice, however, even within the one year period, the longer the children stay, the more they plant roots in Israel, and the greater the risk of the defending parent proving that the other parent has 'acquiesced' (resigned himself to the abduction) which is a legitimate defence. The sooner a child abduction plea is started, the greater the chances of return are. Parents often waste time negotiating and getting toothless orders in their home countries, before taking action under the Convention.
Convention In Action