Auto Air Conditioning & Heater Repair: auto air, releasing some pressure, vacuum pump

Question
a/c blowing warm...  checked pressure and is very high at about 150.  Releasing some pressure shows (by smell) that it is mostly air.  this happened last year also.  Pro did something but said it may not last (he was right).  I released a lot of the pressure and got a can of 135 in it, but probably not enough.  I guess I should have released even more when engine hot, then waited for it to cool down.  If I am okay with so-so cooling, is fullevacuation necessary?

Answer
150 on the HIGH or LOW side ?. You need a set of A/C gages to see what the pressures are running at.

There is no such automotive refrigerant as 135.

I would empty the system, replace the orifice tube, evacuate the air from the system via a vacuum pump and then add fresh freon  to the manufacturers specifications and then check for leaks.