Can you double check Foreman version? This is way too old version! We have been working really hard on optimizing facts, but generally - yes it will grow. It will grow a lot, we store all info in Postgres including facts, reports or audits. It’s all stored in normal form with many associations, therefore many indices are needed so expect a lot of stress to your Postgres.
More modern versions of Foreman (1.17+ I think) has a fact filtering capability, you can filter out some uninteresting facts which can dramatically help to decrease load. For example if you have many network cards (e.g. containers or hypervisors can have hundreds of virtual bridge interfaces) this can create a lot of records.
Please consider sharing with us more details from your deployment: Tutorial: Hardware requirements for Foreman deployments