Circuit breakers are not designed to be used as switch on a daily basis.
Circuit breakers can be replaced if brand of circuit breaker box is still available, for example Square D or Sylvania.
Turning off breaker is not fire hazard unless metal cover over box is missing and spark jumps out from loose wire or shorted breaker.

Turning off AC-heat with programmable thermostat is best choice.
Turning off breaker to oven, washer, dryer will save only if those appliance have electronic clock, however the standby cost for clocks is small.
Standby cost for 10 electronic clocks equal about $15 per year at today's prices.
Other electronic standby: your TV and satellite box and computer monitors and paper shredder have much higher standby consumption and should be turned off using switch or surge protector.
Turning off circuit breaker to water heater is a good way to try water-heater-timer for free >>> for example leave water heater on full-time for 1 month, and compare bill with month when water heater breaker was off >> assuming both months have same outdoor temps so incoming water temps and other factors are same.