Is it possible to conserve power by using touch key detection intermittently?
Yes that's possible.
I don't know exactly what size display screen you mean, but generally speaking, the CTP drive voltage is 2.8v, the logic voltage is 1.8v, it depends on your touch screen drive IC, and then the software adjustment.
If you have a small touch screen, I suggest you refer to Topfoison, which will provide detailed solutions and a full set of references.
I hope that was helpful.