I'll take Local History for 1,000,000 , Alex

What Bad Thing might happen if set the row limit of local history to be some huge number, like 1,000,000 ? Memory issues? CPU issues? Scanning issues? loading issues?  Does it do something smart like "load the last 100 lines, then fetch more on demand ? Does it try to keep all local history in memory? Am I OK doing this , except perhaps for  the disk space it might eat (and how much might that be? )

TIA!