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Is it smarter to buy a small amount of an ETF every 2 or 3 months, instead of monthly?
I personally invest in 4 different ETFs.  I have $1000 to invest every month.  To save on transaction costs, I invest that sum in only one ETF each month, the one that is most underweight at the time. For example, I invest in XIC (30%), VTI (30%), VEA (30%), and VWO (10%).  One month, I'll buy XIC, next month VTA, next month, VEA, then XIC again.  Eventually I'll buy VWO when it's $1000 underweight.  If one ETF tanks, I may buy it twice in a row to reach my target allocation, or if it shoots up, I may skip buying it for a while.  My actual asset allocation never ends up looking exactly like the target, but it trends towards it.  And I only pay one commission a month. If this is in a tax-sheltered account (main TFSA or RRSP), another option is to invest in no-load index mutual funds that match the ETFs each month (assuming there's no commission to buy them).  Once they reach a certain amount, sell and buy the equivalent ETFs.  This is not a good approach in a non-registered account because you will have to pay tax on any capital gains when selling the mutual funds.