On average, Accounting can double the number of logs in your environment as the gateway will send an initial log when a connection is opened and another log when the connection is closed to update on how much traffic passed on the connection.
For long-lived connections this can be even more because every ~10 minutes by default another update log will be sent with the traffic info up to that point. The update logs may be smaller in size, but there is still overhead and updating logs in the log server is more compute intensive than just adding logs.
Having said all the above, many customers do use Accounting but you need to make sure the log server is sized properly.
Another way to significantly reduce load and amount of logs is to leverage "Session Logs" instead of "Connection Logs". This is a setting in the detailed Track options of the rule (similar to Accounting). Instead of sending logs on each connection, the gateway can send an initial log on the first connection and then just accumulate data on subsequent connections that have the exact same match criteria, and only update the session every 10 minutes.
On very frequent and short-lived connections such as DNS, NTP and often http/https this can significantly reduce the volume of logs, with minimal sacrifice of information. Even queries will be faster because there are fewer logs to scan.
You can keep Accounting when using Session logs and you will have the total traffic info on the full session (which includes all similar connections).
