I tend to use 2 to 3 soaps in a regular rotation. Currently I've been using MWF, a test soap, and the third one, which seems to be somewhat 'spur of the moment.' Sometimes I'll simply stick with a 'top performer' and only use that particular soap for weeks. I try not to dwell or worry too much about a well-defined rotation… Heck, even a cream may find its way in some mornings….
While I have around 11 soaps/croaps(TSD, Rays of Colorado, VDH Delux, Van der Williams, Pyrate Cove, Razor Rock, Crabtree & Evelyn, plus 3-4 creams. I tend to be somewhat regimented some might say anal and so I don't embrace change often. So when something works I tend to stick with it rather than rotate. My soap of choice for over a year has been Arko. My only wish is that it would come in a few different scents or at least in almond.
I usually pick a razor & soap or crème or both before I go to bed. Hardly ever is it the same as the day before. I do really like ubelathers so I use both soap & crème a lot. I have about 20 crèmes and over 100 soaps so my choices are many. Luckily for me my wife enjoys soaps and crmes also so she never says that I have too many but does ask me to buy another when she see's a new one she may like
My rotation is random although I have some favorites, I have over 100 soaps with about 75 of them being soaps that I will use more than once. I have to be realistic and trade/sell some of them. The artisan soap makers are getting better and better and it is driving me crazy. Oh well....
I'm in the whatever mood I'm in camp. I'll generally use a menthol on Monday, but even then I have several I can choose from. If I know I want to wear a certain A/S or cologne I may choose a soap that will complement it, but that's probably just an unnecessary process as I don't think the scent of any soap lasts long enough to matter.
Picking items for SOTD is the starting point. I'll usually try scent based themes to match a soap/cream with an aftershave. Using Tabac on Tuesdays is really the only strict rotation I follow. If it wasn't for choosing my "planned" SOTD the night before and posting the pic, I'd probably be late for work each morning trying to decide
I don't have as many soaps, but I close my eyes and reach into the cupboard. The soap that I touch first wins!