CO2 bottle pressure gauge

Hi, sometime ago there was a discussion on the list concerning the usefulness 
of CO2 pressures gauges measuring the pressure of the CO2 bottle to be able to
detect early if the bottle is empty. I think the consensus was that because
CO2 is a liquid in the bottle under the high pressure the gauge would show
full pressure almost until the bottle is empty and then fall within several

Just to share my experiences:
I saw a continuous falling of the pressure indicator from full pressure to zero 
pressure since 4 weeks now and today I can guesstimate ;-) that the bottle will 
be empty in 3-4 days. So I find it really useful to plan the refill. 
However, I had to adjust the output pressure of the regulator more often 
recently. Strange thing was that the output pressure was increasing more and
more. Any explanation for this?

My setup: 1.5 kg bottle (pls. don't ask how many lbs.) and Dennerle Profi
2000 regulator with input and output pressure gauges.

Greetings Andi from Munich, Germany.