Your comments

I think I figured it out.

I was using my bookmark of https://[instance/name] open the site. Using this forces TFA every time.

However, this URL does not seem to force you to TFA every time.

However, by using this URL, it's a few extra clicks to get to my sessions.

Cloud Based. Just a basic standard setup - I joined earlier this year and haven't really customized much at all.

Yep, using Authy - not sure how Google TFA comes into play, if at all.

Maybe I'll try disabling TFA and re-enabling it.

Version 6.4.15361.6527.  TFA client I use is Authy - but that shouldn't make a difference.

This has been happening every since I joined, so I don't think the version number has had any effect either.

Every time I login, I have to do TFA login, even if it's within 24 hours. 'Trust this device' doesn't work.  And this is for Firefox. Regardless of what PC I am.

Checked my TrustDeviceExpireDays. It is set to 30.

Drives me nuts.