Regrettably there is still no single standard for air quick connect male and female pieces. There are about four main historical ones, with the so-called "type M" manual quick connect having current market dominance. There are so-called "universal" designs which claim to accept anyone's male quick connector, and of course those can be more prone to leakage than the others over time because they try to sop up too much of the required tolerance between the metallic parts using soft goods (O-rings).
Using a 200-400 bar Swagelok stainless steel quick connect for air supply to tools is the equivalent of swatting a fly with a sledgehammer. It is also not a guarantee of an increased number of cycles to leakage. These quick connects are generally designed for and used for clean dry gases such as those supplied from compressed gas cylinders.
A normal brass quick connect intended for air, of the single shut-off design, should be more than adequate. Get connectors made for air by a reputable manufacturer (Parker etc.), and most importantly, get all the male and female parts of the same brand. Apparently, the number of ball bearings in the receiving locking mechanism also affects the leakage reliability. More balls keep the hose from pulling the connector out of axial alignment, reducing leakage. The steel male fittings tend to be more durable than the brass ones, and the use of worn or out-of-tolerance male fittings tends to lead to leakage of the female connectors which are the parts that cost money.
There are two basic styles of single shut-off quick connect intended for air: one requires the user to pull back the locking collar on the female fitting to insert the male fitting (sometimes called "manual connect"), and the other that doesn't- the male fitting can be inserted directly (sometimes called "push to connect"). The latter design is quicker and more convenient to use.
When the female quick connects start to leak, you throw them away and replace them with new ones. They cost so little that they're generally not worth repairing. If air leakage matters to you- and it should because it can cost significant money and energy- you do the periodic maintenance to replace them. If you have a 40 hour/week operation, an easy solution is to shut off your compressor during off-hours with a timed relay to reduce that air leakage when it isn't earning you any money.
