Store refresh intervals in a common place

[DL6ER]

What does this implement/fix?

As per the title: Store all the relevant refresh intervals in a common place for easy editing and possibly future programmatic adjustments. See Discourse for reference.

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Related issue or feature (if applicable): N/A

Pull request in docs with documentation (if applicable): N/A

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[rdwebdesign]

It looks like to be working as expected.