TTL tweaks

I've been reluctant to do (some of) these changes in a patch-version update, so this has been hibernating, but let me open a MR already.

Fixes #127 (closed); fixes #736 (closed). (and other TTL-related changes)

The earlier choice was applying TTL bounds only when caching. That makes some sense from implementation point of view, but I can't see any motivation to behave that way and treat the first answer differently.