I dump as much as I can into my portfolio every paycheck, so every year I end up with a little bit of short term capital gains from dividends from mutual funds bought in that calendar year in addition to a growing amount of long term capital gains from dividends from shares I bought in years past. So far it just hasn't been enough in taxes to worry about. I honestly am annoyed more by having to fill out the forms then I am by paying the money. First world problems right.
Some funds deal in weird stuff and have non-qualified distributions regardless of how long you've held the fund, so you get to pay taxes on those like ordinary income too. For a taxable account you therefore want to pay attention to that after-tax yield on the info sheet.
I'm only in for about 150k invested at this point, only around 22k was purchased within the last year (in taxable accounts) and choose funds that are low on the dividend payout, so maybe it matters more if you've got bigger quantities/different funds.
I still wouldn't think of it as a mistake though. If you think of the invested dollars like employees and the taxes like overhead, there's probably more risk in waiting to put someone to work to slightly reduce overhead than there is in putting them to work right away and paying the extra overhead. I'm also suspicious that if you managed to buy a fund that paid out only once a year, and you bought it the instant after that payout happened, you're going to get hit with a non-qualified distribution the next year when it pays out. I *think* it's unavoidable.
It ends up being a similar discussion to the, should I lump sum invest or dollar cost average?
https://pressroom.vanguard.com/content/nonindexed/7.23.2012_Dollar-cost_Averaging.pdfThe market will do what it will do, the IRS is going to get it's cut, save all you can.
Good luck!