How often should I DCA into Syfe and Stashaway? If I were to do it as frequent as daily, would I incur more charges?

The management fee charged on Syfe and Stashaway are based on the total value of your portfolio. As such, the frequency of your investment would not result in you incurring more charges. (i.e you are not charged when you deposit or withdraw from the account)

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If you still believe in the performance of the funds in the long term, you should continue to invest in them.

If you do not have a firm idea of how often to invest through DCA, perhaps, you can try investing monthly. While you can invest daily/weekly to take advantage of dips it may potentially lead to disastrous market timing.