Spring Beauty

With the flowers in bloom, I borrowed my office's digital camera for the weekend. The crocuses are Crocus ancyrensis 'Golden Bunch'. There are also a couple of pictures of snowdrops (Galanthus nivalis). For some reason, these have not done well. I planted ten corms in October, but only five have produced foliage. Two of these are blooming, but not very profusely. Does anyone know anything about snowdrops? Will they slowly increase in vigor, or will they weaken in subsequent years?