My question:

Given that biofiltration is now exclusively performed by plants and
in-tank bacteria, what should I be careful of? I try not to disturb the
gravel unnecessarily, and scrape only the front glass. The tank is
heavily planted, with a nice carpet of dwarf hairgrass filling in. I
haven't vacuumed in 14 months.

Thanks!

I'm curious, do you have fish in there? What's the load like?

In an established tank, there is good bacteria everywhere. In the gravel
especially.

Funny, I kind of have the opposite view you have. Since having a wet
dry, I've decreased the amount of mechanical filtering and increased the
fish load. I only use a pad to catch the large stuff my filter sucks in.
I do frequently change water, but I hardly ever clean the gravel.