Why does sAdhanA seem to be taking so long to bear fruit?

Aim for cessation of thought but the apparent passage of time between this resolve and its permanence may seem long.

In the Bhagavad GItA 6.25 SrI KRShNa says

शनै: शनैरुपरमेद् बुद्ध्या धृतिर्गृहीतया ।

अअत्मसंस्थं मन: कृत्वा न किञ्चिदपि चिन्तयेत् ॥

Slowly, slowly one must withdraw by degrees, by the buddhi held with firmness.

Having established the mind in the Self, he should not think of anything else.

My father used to draw the analogy of samsAra with a silk dress thrown on a brambly bush. It can only be withdrawn gently and with great care.

Purusha is the silk dress and the brambles are the guNas.

Dare I disturb the Universe? as T. S. Eliot wrote.

Yet if the "I" dissolves, then everything is ok.