ive never had a problem with trickle vents.when i first switched to WFP everybody on here kept saying they can cause dirty runs etc but ive never found that to be the case.
Some do and some don't, I clean windows where the vent is on the bottom of the opener ( half way down the window) so you have no choice but to soak them, for obvious reasons they are well sealed but even if they weren't the vents sit far enough out
so that if they where to leak water it wouldn't drip onto the glass.
Personally I don't put water near vents even though I know there are some on my round that I could probably get away with,
a quick rub with a damp microfiber over the brush guarantees quality needed or not.
Then like yourself I'm a price over numbers man.