The temperature increase created by the pressure rise as a bottle is filled will be greater the lower the start pressure, so having your bottle refilled before it gets too low will result in a better fill due to less heat rise. Run it really low and the filled pressure will be reduced more by the additional heat build up. This negates the point of running it really low before refilling.
I use GoDive at Derby, £3 upto 3L and £4 above 3L, they don't use a cold water tank so I don't get a full 300 bar but always in the region of 270-275 after it has cooled which is about as good as can be expected from a fill and go service without letting it cool and topping up again.
They also stock quite a lot of shooting related stuff, silencers scopes clothing pellets rifle and pistols. A good shop that has always been A1, Very good prices on new bottles too!
HFT, for people with only 2 buttucks!
VooDoo TwoTwo The next chapter.