I have two rejections for initial contributor application in last six months. My next turn comes on 19 August. My question is what sort of time frame SS follows for applications. Is it like IS where every failed attempt offers you problems for next and it becomes extremely difficult? Does SS has standard one month or something like that specified period for next application or it will become one year ban after few failed attempts?

IS offered me six months of ban and I cannot apply there. My worry is SS may fall in same space.

based upon my experiences SS doesn't punished you as bad as IS. I failed my first 2 attempts on SS thus don't sweat it. I used the ones that past from my first 2 attempts as well for my 3rd attempt.