is there a way to check how many days left to reach next stake payout in the wallet?
It is a random. No progress. Every pile can find block at every round but bigger pile have more chanses. It may happens now or throu the monts depends how much diamonds you have. You can roughly calculate, using the theory of probability.
when in roulette number 0 come?
its a 1(0)to 37(36) chance
does it mean each 37th time 0 come?
no
lucky streaks unlucky streaks hide the statistic facts
fact is if the timeframe u analyze it is long enough
1/37 of the results will be 0
same for POS
even if statistic can estimate 200 DMD mint on average once a week a 0.82 DMD reward
it can happen u have 5 weeks and find no block at all
same as it can happen in roulette that there is 10 time red in a row
even if statistic say only 50% of results are red