Can 7 day programmable thermostats typically be programmed with each day the same without having to duplicate?
Sounds like you might want to trade in the 7 day programmable thermostat, for a 5-2 day one. A 5-2 day thermostat allows you to set one program for weekdays (Monday-Friday), and another for the weekend (Saturday, Sunday).  That way you'll only have to change one or two programs, instead of 7.

I don't think they make 1 day programmable thermostats, though who knows what you can find on the internet. You may want to consider a non-programmable thermostat, if you don't mind managing the temperature changes manually.

You also might want to read the manual for your thermostat, looking specifically for override and hold.  Typically, if you manually adjust the thermostat, it will maintain the new set point until the next part of the program starts. While the hold feature, should keep the modified set point until you tell it to stop (Run).