Not as far as I'm aware - I believe they're flushed out periodically or once a specific quota is reached, whichever is sooner, to contain consumption, so reporting against the [syslog_transaction] table will be limited to the dataset available.
An alternative is to set up a business rule against an "insert" operation of the [kb_use] table (or an "insert" operation on [syslog_transaction], filtering by URL containing "/kb_view.do") that injects the required data into another table, so you've got an audit table you can report against. Although this goes against the idea of having a single source of record, any truncation of the transaction log table won't affect this audit table - but you may want to keep an eye on just how large this grows.
I would have thought the [kb_use] table ought to work for what you need - try creating reports against that.
