This seems like a moot point as Adventurers will be changed, but here is the data from one test I did with Big Money.
Adventurers(v0.1) - Cost $3
(1) Silver, (2) Adventurers, (3) Silver, (4) Gold, (5) Gold, (6) Adventurers, (7) Province, (8 ) Gold, (9) Gold, (10) Province, (11) Gold, (12) Duchy, (13) Province, (14) Province, (15) Province, (16) Duchy, (17) Province, (18) Nothing, (19) Province
4 Provinces, 1 Duchy - 14 Turns
8 Provinces, 2 Duchies - 20 Turns