Definitely - this is a must.
As you say, it enables you to make your service fit so that they have a good time and come back. I find out what they like me to wear, how they like to start (slow or straight down to it) I offer anal and it helps to keep a note of clients that want this - so I can prep and douche or save time by not doing this if it is not their thing. I can also avoid agreeing to anal if they are too big or do it too hard. I also make a note of condom fits and if kissing is OK or not on. When they share what they like you to wear, not only can you wear that thing but you can make out that you bought it just for them (even though I did not!)
I have all their phone numbers on my work phone and I give each one a client number and show their name (I have over 100 of them) - then I can quickly look them up in my book when they call and make the conversation really personal (even if I can't remember them!). Just make sure that they can't hear you turning the pages of the book
I also have a similar system of recording numbers of punters I want to avoid
I once worked in a customer service call centre and got the tricks from them - at that place, the phone was connected to your computer and as soon as the phone rang, it brought all that customer's details, last jobs etc onto the screen.
I think most do this.
Sammy