When Quantity Pricing is enabled, you can end up with the "effective" item count growing exponentially. This will increase sync times, perhaps even to the point of timing out and/or causing "concurrent request" issues which will make most of your terminals fail the item sync.
To illustrate this, say you have 10,000 items with 4 price levels and 10 of those items have 5 levels of Quantity Breaks.
Using the formula:
i(tems - Items with qty breaks )* price levels + (items with qty breaks * price levels * quantity breaks)
(10,000 - 10) * 4 + (10 * 4 * 5) = 40000 + (200) = 42,000 "effective" items