So-called expert indeed, he might as well have not put a figure on it. And most tyres of any description will last much longer than that. I had over 4k on my first set of Schwalbe Durano Plus on the Viner before the rear needed replacing (and that was due to being run underinflated); the front is still going strong. Well over 1500 on the Squadra's set so far.
Schwalbe's estimates on longevity are from 2,000 to 5000 km for their standard tyres (1200-3100 miles approx), 6,000 to 12,000 km (3600-7200 mi.) for most Marathon series tyres, 5,000 to 9,000 km for the (lighter & faster) Marathon Racer & Supreme, up to 15,000 km for the Marathon Plus (!!). For the Ultremo ZX- a race tyre, mind you- 3,000 to 7000 km.
The OP is unlikely to need new tyres just yet if she looks after them properly (i.e. keeping them at the right pressure & removing debris).