Tax management in the future

Hello everyone,

So I have been having this thought for a while regarding how could one manage capital gain tax in the future (let's say 30 years)

To make things clearer, I will present a simple example. If I invest X amount of money in some kind of ETF in the next 30 years starting tomorrow, with recurring purchases every month.

After given time, I have decided to get the Y amount of money out of the brokerage account ( with profit or not doesn't really matter). Knowing that some countries have tax breaks for owning an investment for more than let's say 10 years, how hard would it actually be to manage all the purchases in all this period? Would I have to keep track of every investment ever made in order to get the tax benefits?