I shave because hairs happen to grow out of my face. I'd rather they didn't, but they do, so in the immortal words of Edmund Blackadder: "Needs must, when the devil vomits into your kettle."
I shave about 2 days after the previous one, give or take a few hours. Minimum of a day and a half gap, 3 days absolute max. Suits me for now, at some point I may experiment with shaving every day for a week and see how my skin likes it.
Time of day varies due to working shifts. Early shift = mid afternoon shave, late shift = 9am shave. Try to shave whilst have house to myself as its simply more relaxing. Late night shaves can give a nice relaxing feel when retiring for the night, but I prefer to shave during daylight generally.