Is the Rate of ruin .i.e.where prob(ruin) changes fastest, affected most by the number of consecutive losses?

If so, is there any condition or optimal N, maximum no. of consecutive losses to indicate a good time to exit the game?

In a bias coin toss game where prob(head)=0.7, what is the probability of 30 tails clustering (not necessary consecutively) in the first 50 tosses out of 100 trials?

Appreciate any suggestions.