I've done some long term measurements on my GPSDO. The GPSDO has a RS232 based simple command interface.
Commandline interface
It has a bunch of commands available. I assume, that the following commands provide information on the GPSDO internal control loops for temperature and GPS.
Status command "diagnostics:loop?"
This command provides the following output:
UCCM-P > diagnostic:loop?
-------------------------------------------------------------------------------
9/1/2016 10:43:51
-------------------------------------------------------------------------------
LOS MEAS NCO STATUS WEIGHT PBUC FBUC DBUC LBUC IBUC G M TC
-------------------------------------------------------------------------------
0: 1 0.000e+00 0.000e+00 0x07AC 0 700 700 0 0 0 2 4 29
1: 1 0.000e+00 0.000e+00 0x068C 0 700 700 0 0 0 2 14 226
GPS: 0 5.988e-08 6.357e-08 0x0000 1 ---- 1000 1000 ---- ---- 3 6 31
-------------------------------------------------------------------------------
freq cor = 6.356560e-08
phase cor = -2.000000e-11
gps phase = 1.366667e-08
temp cor = -3.911350e-11
Using this command, I extract these values for "freq cor", "phase cor", "gps phase" and "temp cor" and feed it into my sensor network. Each diagram shows the data for the last 15days.
If someone has more information on the meaning of these value, please give me a hint!
Frequency correction
At the beginning and at about day #5, you see a restart of the GPSDO due to power failure. This line is contantly rising - no idea why this happens. If someone has a clue, feel free to contact me!
Temperature correction
This value is reverse proportional to the room temperature of the GPSDO. The warmer the room, the less the main osciallator has to be heated.
GPSPhase
At the beginning and at about day 10 you see a restart of the GPSDO due to power failure. This value is more or less stable - means a horizontal line.
Phase correction
This value is more or less stable - means a horizontal line.
GPS:SATellite:TRACking:COUNt?
UCCM-P > GPS:SATellite:TRACking:COUNt?
+4
From this command, I extract the number of tracked satellites. 
The diagram also shows the data for the last 15 days.
system:status?
UCCM-P > system:status?
-------------------------------------------------------------------------------
090-03861-03 serial number W561002488 firmware ver 1.0.0.2-01 LINK mode
-------------------------------------------------------------------------------
Reference Status __________________________ Reference Outputs _______________
Ref 8KHz 0: [LOS]
TFOM 2 FFOM 0
UCCM-P Status[ACTIVE]
>> GPS: [phase: 5.00e-09]
ACQUISITION ................................................ [ GPS 1PPS Valid ]
Tracking: 4 ____ Not Tracking: 5 ________ Time ____________________________
PRN El Az C/N PRN El Az GPS 10:46:26 01 SEP 2016
18 38 131 40 10 17 165 GPS Synchronized to UTC
21 64 66 35 16 63 290 ANT DLY +0.000E+00
26 69 204 43 20 32 62 Position ________________________
29 13 91 35 27 37 286 MODE Hold
31 5 204
LAT N 48:xx:xx.xxx
LON E 9:xx:xx.xxx
HGT +xxx.30 m (MSL)
ELEV MASK 5 deg
-------------------------------------------------------------------------------
tbd