Inspired by a discussion with John a while back, I decided to try moving some of my pressure regulators (particularly for smaller/touch-up guns) "off-gun". My guns were already set up with 6 to 8 foot, 3/8" diameter "lead-in" hoses that are directly attached to the gun via swivel fittings (no quick-connect fittings). Moving the regulator is therefore a simple matter of moving it from between the gun and swivel fitting to the opposite end of the hose. Doing so makes the gun much more maneuverable in tight spaces.
The main concern with this sort of configuration is pressure loss. HVLP conversion guns take relatively high airflows at low pressure, and that's basically the worst case for loss in a hose (just as low-voltage, high-current is the worst-case for transmission loss in a wire). The issue is compounded by the fact that it's flow-dependent - adjusting, say, the fan valve on the gun can change the flow rate and therefore the pressure drop. This turns out not to have been as serious an issue as I thought. though. Gates has a handy pressure loss calculator here, and for a typical conversion gun taking 10 scfm at 20 psi, the loss amounts to 0.16 psi/foot, or ~1 psi at 6 feet for a 3/8" ID hose.
Note that smaller hoses are very, very bad news. The corresponding loss rate for a 1/4" hose is 1.37 psi/ft (i.e. about 8x worse than the 3/8 hose). Conversely 3/4" hoses only lose 0.004 psi/foot under the same conditions, which is why they're sufficient for non-conversion (i.e. turbine) guns.
All in all it's a positive change IMO. I have to reach a bit further to adjust pressure, but the maneuverability benefit is worth it.