Do you invest monthly or every 2-6 months? [IBKR]

Hi, I’m looking to add 200-300 monthly to IBKR (EU-based). Currently thinking 70% SPYL (SP500 Acc) and 30% VWCE (All-World Acc). Do people invest monthly or what’s the best frequency? Considering experience in average returns vs commission per trade. I’m asking as IBKR commission per trade: “European: Tiered is usually 0.05% of the trade value with a minimum of €1.25, while Fixed is 0.10% with a minimum of €3.00”. Edit: Trade Republic seems to have a higher cash protection and 0€ trade commissio