Small correction: it is more accurate to assume that difficulty adjusts every 14 / (1 + DifficultyIncrease) days (target time is 14 days, the new difficulty is based on the average hashrate of the previous period). If you multiply this value with the sum of the infinite series you actually get a very elegant result:
14 * CurrentDividend / DifficultyIncrease
(for full derivation see this post: https://bitcointalk.org/index.php?topic=228327.msg2493461#msg2493461)

So with a 10% increase per readjustment, you can expect 140 times the current daily dividend from DMS.MINING.