arduino stability

we want to design a product based on atmega328p-pu, i have one doubt will it work 24*7 365 days? actually we are designing water level controller and home automation , we will give constant 5v power supply and will use optocoupler to switch the relay,we will maintain temperature between 15c to 45c , please reply As soon as possible .

will it work 24*7 365 days?

As long as the power is not interrupted, yes. The Arduino does not need weekends off, or get sick leave or vacation.