I have 17 cards, not a ridiculous TCL (around $65k), and I carry my Gold charge, BCP, CU Visa, and Disco cards daily. The rest are accessible for when their intended uses arise. The ones I listed are my daily used cards, where the vast majority of my spend goes. I use all of my cards at least every couple months though, except Firestone which I used today for an oil change on one of my cars but which hadn't been used in five months (statement cut today and thankfully it is still open).
Like another poster up above, I use a spreadsheet to track everything. I track balance, limit, available credit, aggregate and individual usage percentages, statement and due dates, CLI dates and amounts, a running tally of how much my total required payments are at any given moment, and reward balances. The spreadsheet calculates everything based on balance and limit, including a separate table that shows the balance on each that equates to a scoring threshold, and one that shows the paydown amount needed to cross the next lower threshold. (I'm an engineer, can't help it - I like numbers). It even color-codes cells based on how soon payments are due, usage, whether or not that month's payment has been made, etc.
All that being said, I typically pay as soon as the statement cuts on the 2-4 cards per month that post a balance, so the requirement is handled immediately, and then I'll throw extra money at them before the due date as the month goes on. The majority are all paid to zero before the statement cuts. It makes it pretty easy to manage it all as long as my spending stays under control and I don't start to amass balances on multiple cards, which I used to do (hence all the calculations and such in the spreadsheet), but which is a thing of the past as of this year. My reported usage stays between 4-6% now, typically under 5%.
