Disklavier

I have a question about regulating my house temperature during the 
winter months and the potential effect this may have on my 
Disklavier MX1Z upright piano.  The piano is not located near any 
heat sources, in direct sunlight, near an outer wall, etc., or 
anything that would directly affect the piano in an adverse way.
 
I live in the 'great white north'.  Actually, I live in Edmonton, 
Alberta (Canada).  Hockey fans will know about Edmonton as Wayne 
Gretzky played here during his climb to fame.
 
Edmonton is geographically situated at:
    Latitude: 53 degrees, 18 minutes north 
    Longitude: 113 degrees, 35 minutes west
 
Here's our annual meteorological statistics (temperatures in 
Fahrenheit):
 
         Average    Average   Warmest  Coldest  Average      Average
Month:    High:      Low:       Ever:   Ever:  Dew Point:  
Precipitation:
 
JAN.       19         2          46      -49       3         0.9
FEB.       23         4          55      -40       6         0.6
MARCH      34        16          63      -29      16         0.7
APRIL      50        29          86      -18      26         0.8
MAY        62        39          90       18      35         2.0
JUNE       68        46          88       30      45         3.5
JULY       71        50          90       36      51         3.4 
AUG.       69        47          91       25      49         3.6
SEP.       61        39          93       16      40         1.9
OCT.       51        29          83      -15      29         0.5
NOV.       31        13          64      -29      15         0.6
DEC.       21         3          48      -47       6         1.0
 
(http://www.usatoday.com/weather/climate/northame/canada/wedmonto.htm
)

My house has a forced-air furnace that burns natural gas.  My annual 
combined natural gas + electricity costs run about CDN$1500 
(depending on fluctuating prices and severity of annual weather).
 
Like many who live in cold climates, I use a programmable furnace 
thermostat to vary the temperature throughout the day. The program 
is set to provide a 'comfortable temperature' based on whether 
anyone is typically home at the time, for overnight sleeping, etc.  
Programmable thermostats are quire common and are used to save $$'s 
and equally to conserve energy (natural resources).
 
To put this into context, here's my thermostat's winter heating 
schedule:
 
Day:           Time:         Temperature:
 
Mon-Fri   7:00am -  8:45am   68.0F (20C)
          8:45am -  5:45pm   64.4F (18C)
          5:45pm - 10:45pm   68.0F (20C)
         10:45pm -  7:00am   54.4F (18F)
 
Sat-Sun   8:45am -  11:45pm  68.0F (20C)
         11:45pm -   8:45am  64.4F (18F)
 

When someone's home the temp will often get bumped up to 69.8F (21C) 
for comfort. Also, if we're traveling, we'll hold the temp at 18F 
while we're away.  The humidity in my house typically varies between 
35%-38% during the winter.  Of course anything that creates humidity 
(cloths dryer, etc.) will temporarily increase the relative humidity.
 
Okay then.  With all the foregoing information as background, and 
with regard to my piano, should I reconsider using my programmable 
thermostats and simply hold the temperature at 68F all winter?  Then 
again, maybe I should move to a warmer climate!
 

Robert