After $8$ years of owning the spa, David$$s investment $($from Question $3)$ matures and he decides to use this balance to build an addition to his spa. He makes weekly withdrawals from his investment account to finance this new venture.

$4.$ David withdraws $$6,000$ at the end of every week for the first $3$ years to establish and market the expansion. Afterwards, the withdrawals will lower to $$3,500$ at the end of every week. Throughout this period, the high$-$yield investment continues to earn $9\mathrm{.}8\%$ compounded daily. What is the total length of time that David will be able to make weekly withdrawals for? Express your answer in years and months.