It is clear: the sooner the bonuses are credited to your account, the longer the money can work, thanks to the so-called compound interest effect.
You must always apply for the bonuses, even if you assume you can claim a special expenses deduction. Otherwise, you will lose part of the funding. This is because the special expenses deduction only gives you a tax advantage on the amount that exceeds the Riester bonuses. The bonus is always counted as a tax benefit already received.
It does not matter whether you receive the bonuses or not. However, if you have submitted the permanent bonus application to your Riester provider, you do not need to worry about this.