Tax increase mainly depend on the amount of goods traded (in Europe or Africa or Port Royal or by Custom Houses).
So if you don't trade (enough) goods you won't have tax increases.
Trading with Natives or using Domestic Markets will not lead to tax increases.
It is
not simply a matter of time.
(It never was in Vanilla either.)
Since I don't know you style of playing, I can't say if your game behaviour is "correct".
In my last game (about 1 month ago) everything was working fine considering tax increases.
(I usually build up gigantic Empires with huge fleets of ships travelling between my colonies and Europe.)
And of course in Marathon, you need more goods traded for tax increases.
(Everything is slower in Marathon.)
I don't Play Marathon myself.
But other peopel told me, that they do and nobody reported bugs about tax mechanism.
So I am totally convinced that tax mechanism is working as supposed in
Release 2.4.
Maybe it is just nor working as you expect it to.
Unless of course you messed with XML balancing related to tax mechanism.
But that would then not be an issue of the mod.