with such a long loop length (and fewer loop cycles) like you suggest, I can play a full 6 or 7 minute track with no audible drift from the looped deck.
a much bigger test is looping just ONE BEAT on deck A and playing a full track on deck B which i also tried. I found that a manually beatmatched track would start to drift out after a minute and a half or so (after which it's probably cycled 150 times) - you'd probably never do something as extreme like that in practice though.
if you activate Beat Sync on the deck with the tiny loop, it stays in time for the full 6 minute track.
Hope this helps.