Well, the best thing to use for trials is verified trials: https://wyday.com/limelm/help/trials/#verified
The best thing for "demos" of the full product is also probably verified trials, but you could also use a product key with custom license fields: https://wyday.com/limelm/help/license-features/
If you're using trials then there's no need to deactivate. Also, if you're using custom license fields then there's also no need to deactivate. Just change the custom license fields to "full version" values.