Understanding Autofac lifetime scopes

Passing in a lifetime scope is like passing in the container itself. It resembles the Service locator (anti-) pattern and has exactly the problem you described:
Dependecies become non-obvious.

One thing to ask yourself:
Are you actually having problems with your memory? If not, I wouldn't bother.

Another pointer:
If you have individual services that should be disposed right after usage, use a factory to create them and make your class depend on the factory instead of the service itself.

The usage scenario for lifetime scopes is a little bit different:
They are used when you need a local composition root. I never had the need for something like this in a windows application, but in web applications a Session or Request can require a local composition root.