Yeah, restaurants suck. I too have worn most of the hats, but it was a great experience, especially when I was a waiter. (I used to smoke just a little weed sometimes before a shift, and my personality would open up just a bit wider, so I'd get a bit more talkative and friendly, and my tips were definitely better, and girls would literally give me their phone numbers on the back of the guest check, along with little lovey-faces! Haha!)
I learned how to micro-manage my time. I could juggle 3) 4-tops and a few deuces during a lunch rush, because I was not only organized, but I knew the importance of letting everyone know I haven't forgot about them, and I'll be right back as soon as I grab my other table's order.
I learned a thing I call "slotting-in", that I even use when I'm running a carpentry crew, which has been as many as 10 people at a time- and everyone always has something to do. I'll leave all sorts of tasks that need doing, but aren't top priority, available to 'slot in' for whomever has some time between other things. It works great. "Hey do me a favor- whenever you have a few minutes, and you're waiting on the guys to give you your next measurement, go over and cut out those 4 door plates." This way, a task gets done, but doesn't add any extra amount of time to the job, since it was 'slotted in' to time the cut-man would've otherwise spent waiting on the next measurement to cut.
And in serving, if I had a few minutes, but I knew in about 3 minutes I was going to be busy for the next 10 minutes delivering a large order of food for a table of 6, I may go around to my tables and grab any dishes that were done, which had the extra benefit of me not walking back into the kitchen empty-handed. Collect a few drink orders, while re-filling some water glasses, drop them off at the bar, ask someone to deliver them to table 6 if I was in the middle of serving my other table when they were ready, and go get my food. (So there's a little, ask-for-help as needed in there as well.)
So to the OP, yeah I'm still real good with retaining info, maybe because I got very good at juggling lots of small details in my younger days? Who knows? But I always exercise my brain.
One of the ways I do that is by learning JP solos. So many of them are really interesting (that's a big key to retaining something- it has to interest you), and even though I can't play most of them at speed, I can remember them.
I just this week got a 3-D drawing job, and I hadn't used my 3-D drawing program in a while, but all the keyboard shortcuts I had memorized came right back to me, along with all the tricks I'd learned for how I want my workflow to go. Yeah, I had to go back and draw some things differently, but 90% of it came right back to me.
The day I really start losing my mind, I'm ready to go, whenever it becomes a problem. My mind is my most important tool!