It would indeed delay the announcement of the results. A number of countries do that. Here in Canada, British Columbia does that. However, in cases where the votes are close, it can increase tensions about the election results, concerns and sometimes even conspiracy theories. As a result, it isn't something I have recommended in the past.
However, I have recommended giving an extra week at the start of the election, when the election doesn't have a fixed date. That would have the same effect. There's less of a problem in a fixed-date election, because voters are better able to plan their vote. When there isn't a fixed date, if the idea is to add time, I would put it at the beginning of the election period, not at the end.