Tips on conducting regular-weekly O3s, but on variable time slots

BLUF: I´m interested in learning tips on how to conduct regular weekly O3's, but allowing for regular flexibility on the time slots.

I used to be quite effective and efficient at conducting O3's with all my directs. I even handled a few matrix reports. I kept a live and dynamic flow from week to week and was able to manage all my notes from the O3's in a neat system.  This delivered awesome results for the team and myself.  I'm happy to report that 2012 was a super year for the team and we delivered great results.

So far, so good.

My problem is that during the last quarter things got a little busier and a bunch of us had quite volatile agendas.  We traveled, we had meetings with clients, boss' agendas, etc, that conflicted with the preset O3 time slots.  This got out of hand and we got into the habit of postponing O3s until the following week- to the point that we haven't had regular O3's in weeks. Unfortunately, 2013 does not seem to come with an easier or more regular weekly scenario than 2012. (I've listened to practically all casts and admire how Mark and Mike talk about O3's while traveling.  I have had little success doing O3's while traveling.)

The solution I'm thinking of is to reinstall O3's with the team, but this time without a preset time slot.  I'm looking at having a weekly checklist with all my directs names on it and work through the week ckecking their names off until I have completed the full round.

Does anyone have any advise on this subject?

Thanks in advance!

Raúl- El Salvador