Using infinite series calculations supposing difficulty readjusts every 12 days (CurrentDividend * 12 /(1-DifficultyIncrease)),
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.
The target time is readjusted for difficulty increases that have occured in the past, so if difficulty increases by some amount after the readjustment, that 14 day number should be multiplied by somewhere over (1-%DiffIncrease) to get the approximate date before the next readjustment, this is why the last few adjustments have been at 12 days.
I guess it would be more accurate to say 14 days for a 5% increase, to 12 days for a 20% increase, and then waffle and say 13 days for numbers in between. If this were to be calculated, then DMS.MINING will pay out a lifetime of
0.0364 for 5% Difficulty increase
0.02253 for 7.5% increase
0.169 for a 10% increase
and the 20% number would be the same as the previous post