Did you know that you can browse to your Infusionsoft application and type on the end of it "ClientLogin" to see a place where your clients can login and manage their subscriptions & profile?
Here's an example...
Try that one on your application by putting your Infusionsoft name instead of mine and you'll see that you have one too.
Clients can go in there and update their profile anytime or update their subscription payment methods and even add credit cards to their account.
This is just one example of something that I'm always surprised to find people not using.