There is an option somewhere to disable the auto standby feature. This is in the picture settings menu I think.
edit : old instructions, probably still correct
# Press the Services button on your Sky remote.
# Press 5 for Sky+ Setup.
# Push up twice to highlight Auto Standby.
# Push left (or right) once to change ON to OFF.
# Push down once to highlight Save New Settings and press Select.
# Push the Sky button to return to whatever you were watching
Originally it was that your box would only go into standby at night. But I think in the name of green-ness they have extended this to any time of day after x amount of inactivity as Arriba says.
FYI: Software upgrades are done over the air (dish) not over the phone line.