Up until now I've been fairly good at taking a spiro+estraidol at 9am and then another spiro at 9pm.  I have a conference starting at 9AM every day next week, and taking my HRT pills at 8AM would be much more convenient.  How consistent do I have to be with when I take my pills?  Would it be a problem if I switch to 8AM for a few days and then go back to 9?

It'll be fine.

If it is twice a day, then 2hr +/- will not make a difference.  Just don't get the doses too close to each other without checking with your pharmacist. Since it is Spiro, do keep up your hydration routine though.

Good to know, thanks!  I'll continue constantly drinking water