During winter if I'm not working out/training and not going to work, i.e. weekends/holidays,
occasionally I'll not shower every day because i'm not sweating and I don't need to be shower-fresh for any reason, but I will give myself a little "bird-bath" (as my grandmother used to call it

) by washing my face, armpits and personal areas with a washer. Water conservation has always been a big issue in Australia and I grew up on a farm where we bought water by the tank-full so it's kinda been engrained in to me all the little ways you can save water. So if I haven't been doing anything, and if I'm not oily or stinky and don't need to wash my hair, I'll have my little bird bath instead
The only other time I don't shower every day is if I'm really really sick with the flu or tonsilitis and literally not able to get up out of bed to have a shower.
Without wanting to sound crass, for the sake of your personal hygiene I think 3-5 days is really stretching it man. Even if you don't live in a hot climate, even if you don't do much physical activity, even if you don't actually SMELL, there are still quantities of bacteria and fungus that build up on the surface of your skin and in between all every tiny skin fold that you need to at least wash off with a damp cloth every day.