In theory this is useful but in practice I would not expect more than changes at the margin.

An ounce of practice is generally worth more than a ton of theory.

The technical challenges were solved in theory but not in practice.

A thing may look specious in theory, and yet be ruinous in practice; a thing may look evil in theory, and yet be in practice excellent.

An economist is someone who sees something that works in practice and wonders if it would work in theory.

In theory one is aware that the earth revolves, but in practice one does not perceive it, the ground upon which one treads seems not to move, and one can live undisturbed. So it is with Time in one's life.