Deposit them where? Most dependent care plans are funded out of the general assets of the ER. That is, no separate fund. The ER's general assets are enhanced by not having to pay the EE by the measure of the salary reduction elected to pay for the elected day care benefits. When a claim for day care expenses is submitted, the ER pays it out of its general assets. You ought to look at the plan terms to see what is said about the timing intervals (if any are imposed) for submitting claims and what the time lines are for paying them.
If there is a separate fund being used as contemplated by your OP, then there might be a problem.
DoL Reg 2510.3-102(a)(1) provides
DoL Reg 2510.3-102© provides
They are depositing them into a checking account used for the reimbursements. However, until they actually deposit the deferrals into the checking account they will not pay out any reimbursements.