If I ride on a particularly messy or rainy day, I will give the bike a wash. In drier conditions I may do a quick clean every couple weeks, maybe once a year I will use something to shine up the paint. That something is usually some Pledge or car "Quick Detailer" if I am too lazy to walk into the house to get the Pledge.
My bike is 18 years old, and with the exception of one blemish, the powdercoat paint looks the same as it did when I took the frame from the shipping box in 2001.
So, my point is, clean the bike as often as you wish for vanity/maintenance/OCD purposes, but there's really no product IMO that will "protect" your frame's paint over time.