At what point will speed became an issue with the Item Ledger table in NAV?

I'm evaluating NAV and after learning how the Item Ledger table works in inventory and the calculations being done to flowfilter fields for inventory on hand quantities do I need to be concerned about performance issues relating to the number of transactions that may exist for a single part number in the system? If I have a single part number with 100,000 transactions, would that be considered a lot in NAV and at what point could I potentially see issues with performance for reports or screens that display this information?

Also, if I need to access inventory on hand quantity from outside of NAV for reporting, do I have to read the Item Ledger and calculate my own on hand quantity? Are SIFT / flowfilter fields only a C/SIDE (NAV) capability? (New to MS SQL Server also)

Thanks,

Jim