ETF fees are taken by small amounts daily. This makes small changes in the NAV. So they don't track how long you have owned it. Now trading may cost you more or less based on the brokerage you use. Some that offer free trades may charge you for the quick turns.
Ah, so the expense is baked into the price continually? That would make sense.
Been trading stocks for years so aware of fees, Interactive Brokers works great for me. But new to trading ETFs and couldn't figure out the expense aspect.