Thank you Pawel!
Must have been Mr Gemini that overextrapolated some internal defaults from the DataAggregator source code. “GATEWAY_DATA_AGGREGATOR_CLEANUP_TRANSACTION_RETENTION_DAYS: This was introduced to prevent the massive PostgreSQL “bloat” that occurred during the early days of the Babylon mainnet. It targets the transactions, transaction_status, and events tables.”
Nevermind.
From what I read. We should stay away from trying this at home 
It mainly leaves us with this path → If we want to reduce the burden on Stokenet Infrastructure and gateways, we should reset the testnet more often. And “industrialize” the reset process so that the impact is minimal. I am pretty sure that builders will adapt to the new normal quite fast. Where we reset every 3,6 or 12 months. Decision could be handled as two consultation.
Reset or not?
In the case of reset. How often?
With you experience on handling the gateway. What will be the effect on Disk writes when reducing the size to almost nothing and give the system more memory? I assume it will benefit the indexes and reads but will writes stay the same?