Air Conditioning - A/C Vent Temperature?

What should be the average temperature be coming out of a air conditioning vent in my apartment? I don't think our air con is being efficient, the temperature is blowing out at about 70F, should it be much lower?
Many Thanks, Ed

To just say what is the temp out of a Register dont work. You want to take the air temp over the coil. It should be about 18o to 20o temp drop over the coil . At the coil

At standard design conditions, air coming out should be in the range of 55 to 60 degrees to cool the house down, regardless of the ambient house temperature. The unit should be able to cool even air at 85 degrees flowing into the unit down to 60 (at the vent) if it is functioning properly.

Some factors that do influence the vent temp are where the unit is located, where the ducts are, how far the air has to travel, and the air speed. Generally, ducts in warmer areas such as attics will gain some heat (thought not enough to impact cooling performance noticeably). Also, if the blower is set on a low speed or simply does not blow hard, the air will be a bit cooler.

Have the filters been changed on a regular basis? What are the indoor and outdoor temperatures? Was there a change in the way the unit operates? Vent temperature in itself does not determine efficiency. Efficiency is BTU's of cooling per Watt.