Actually - referring back now to your first point; your Organization does include more Meraki gear (you mentioned switches as well as APs, which I'd missed). Any time you apply a renewal, the key needs to include licensing for all the devices you need to keep working. So in my example above, you could still do two separate orders, 3 years and 1 year, but both of those orders would also need to also include the switches and all the APs (and any other Meraki devices you want to keep working).
In co-termination, everything is encompassed by one date - you can't part-renew.
Remember too that an Organization is either compliant or not. If it's non-compliant, it will enter a 30 day grace period (where admins get lots of warnings to fix it). If you let that expire, without fixing, ALL the devices will stop carrying traffic. This is clearly not what anyone wants. Maybe look to catch up with your Meraki account team to go through the detail? As mentioned briefly above, a shift to Subscription licensing might be a good option.