Oracle is going to reclaim idle instances. What's interesting is there definition of idle is not zero use. It sounds like you can keep using the free tier if you switch to pay-as-you-go.
The only interruption I have experienced was following the initial 30-day trial period. I have been the free-tier ARM Ampere A1 resources for 3 K3S worker nodes for over a year now. I did find this note which provides what they consider idle:
Oracle Cloud - Free-Tier Reclamation of Idle Compute Instances
Idle Always Free compute instances may be reclaimed by Oracle. Oracle will deem virtual machine and bare metal compute instances as idle if, during a 7-day period, the following are true:
CPU utilization for the 95th percentile is less than 10%
Network utilization is less than 10%
Memory utilization is less than 10% (applies to A1 shapes only)
Hope this helps anyone who may have been wondering.
Oracle Cloud - Free-Tier Reclamation of Idle Compute Instances
Idle Always Free compute instances may be reclaimed by Oracle. Oracle will deem virtual machine and bare metal compute instances as idle if, during a 7-day period, the following are true:
CPU utilization for the 95th percentile is less than 10%
Network utilization is less than 10%
Memory utilization is less than 10% (applies to A1 shapes only)
Hope this helps anyone who may have been wondering.