I have monthly deposits, and mostly just check balances once a week or so. As for buying funds, yes I could do that, but I'd like a nice mix of large and small cap, domestic and foreign, and the tax loss harvesting is quite handy! This would be far more work than I want to undertake elsewhere.

you'd also have transaction costs to buy monthly and rebalance when needed which would probably cost about the same as the betterment fee.