Test for it + dose depending on demand [which will change over the course of the tank's lifetime].
When I first started using it, I would dose every two or three days, maybe 15-20ml to my 58g. A few years later, I now dose 35ml daily to that same system ... due to change in demand, corals I keep.
In my opinion, dosing daily [or multiple times] smaller portions is a better idea than less frequent/more.
Honestly, I would test your tank [and test newly mixed saltwater, see what waterchanges are doing] for both Alkalinity and Calcium. I tend to watch Alkalinity more - as mine seems a little more variable - I `see' demand more in this IMO.
Perhaps start a minimal dosing regimen of 2-part, I'd `undershoot' at first. Test a few days to a week later - see where levels have gone. If they're remaining about where they started - then you're relatively close to demand. If they fell a bit ... then you'll want to increase dosing.
Keeping some sort of log/record/calendar with these test results is useful IMO. While I don't record `normal' readings anymore ... it's useful to see how demand/dosing is matching over time. [I should have recorded dosing amounts, too]
But I'd work out your demand through a few week to month period of regular testing + regimented dosing ... and check on that regularly thereafter.
In the almost 3 years my 58 has been running, demand has varied a lot. When I've slacked from testing, I've found that levels can get off within a month's time [even with regular waterchanges] ... just my experience. And it's not a linear-type increase in demand - there's been periods where IMO demand fell for a month or so ... and periods when everything thrived and demand skyrocketed.