CloudWatch monitoring

If I disable CloudWatch monitoring for my EC2 instance, will I lose my metrics data ?

No. You will not lose your metrics data even if you disable monitoring. You can retrieve metrics data of your EC2 instance for up to 2 weeks from the time you started to monitor it and after 2 weeks, the metrics data will become unavailable. If you wish to store metrics data beyond this duration, you can use GetMetricStatistics API to retrieve your metrics data.