I use 4' hoses with a ball valve on the end, then another 10" hose screwed onto the ball valve. Each of my 3 hoses is a 3 piece assembly(long hose-ball valve-short hose). The short hoses with a ball valve permanently attached are not a good idea because you can't purge the air out of just the small hose if you keep pressure in your manifold like I do.
I can't stand low loss fittings!
When I disconnect from a system, I open both valves on my manifold briefly to clear any oil, and close the ball valve on the liquid side.
I let the system pull all the liquid out of my hoses and manifold, then close the ball valve on the vapor side and disconnect my hoses. I only loose the little bit of refrigerant in the 10" hoses.
This leaves my manifold and hoses under some pressure from the remaining vapor.
The next time I hook up to a system, I connect my hoses, purge the air out of the 10" hoses and open the ball valves.
I'm loosing less than an ounce of refrigerant from connecting and disconnecting to a system.
Before I got a 2nd set of digital gauges, I used the same set for R-22 and R-410A.
Before hooking up to a system with a different refrigerant than the last one I worked on, I would bleed my gauges and manifold down to 0psi, and hook up to the system, then purge my hoses and manifold with the new refrigerant. Still probably loosing less than an ounce of refrigerant.
Now that I have 2 digital manifolds, I just use one for each refrigerant.
I use that same method when dealing with commercial refrigeration, say a 7 oz critically charged cap tube refrigerator. On the bigger stuff I don't even worry about whats left in my hoses as I am more worried about the damn shrader core getting stuck and leaking.