Nowadays I use it once a month, as here im Brazil we are allowed to sell each month about 5k usd per month without paying tax gains.
That's a really nice law. And the timeframe in which you have been holding your coins doesn't matter? Holding them for one day or one year is treated the same way?
Yes, this tax free can be used even for day trading. If you sell more than 30k BRL (about 5k USD) you need to pay 15% taxes over your gains. If you hold for 1 day, the gains will be small and the tax will also be small. If you are holding for 5 years, the gains will be big and the taxes will be higher.
I think it is a very nice law as well. It is also amazing if you decide to buy something with bitcoin, if it is below 5k USD in a month.