I perform several times a week (not to the same person, of course). At a gig I may perform the effect a dozen times in an hour, give or take (5 minute walkaround sets, that's about right. I don't actually count though).
I got 3, actually, one for my killer ending move; so at a gig, or a crash, I do this every 5-10 minutes or so, depends on how many performers there are, and what type of place/specs I'm performing to.
And one if they ask for another finale...
and the 3rd, if I mess up, lol, so I can cover up for my mistakes.
the last time was in the bank, I was in a long row and I was performing there and everyone was excited and then I performed one of my best card tricks and then everybody screamed.
I guess my answer is be ready always to perform you greatest effects or at least some of the greatest for the simple reason that could get you a gig or you will give an awesome experience for them to remember
I only do three effects with cards and each of them I feel are very very powerful.
Well they are not really effects but more of full routines. I feel that each one of them achieves a certain aspect of what I want to do, and the image that I try to create.
One is a watcher / reader type where I can get inside someones mind.
One is a influence based routine using OOTW and a few other variations.
The final one (my personal favourite) is how I can completly control everything that a person does.
I'm going to add that between chicago opener, more on oil and water, and a TnR...I don't do much with cards.
If borrowing a deck I may do an ACR or card to impossible location...but I don't find myself learning/using cards much anymore. Easier to throw some coins in the pocket, rubber bands around the wrist and maybe chapstick for redline and a pen for 'vanishing pen cap' or x-finger.