I update consistently twice a week and don't see real falls in my stats
FA - FurAffinity
DA - DeviantArt
Tap - Tapas
VK - Vkontakte
WT - Webtoons
AK - Авторский Комикс (Russian site)
I was never staff promoted on any of the sites. There's a tiny chance I got promoted in June on Webtoons, but I didn't see anything, just stats peak. Also that was the month I apllied for ad revenue, so that might cause some interest from the staff. Anyway consistent updates seem to lead to consistent growth. I didn't do anything about FA and DA for the last few months and AK is a tiny local site. So Tapas, WT and VK are my first priority.
As for self-promotion, I don't do too much. Of course, I use this forum (seems to work for Tapas) and Twitter (doesn't really work since have very few subscribers there). I'm registered on TWC and get about 100 votes per month (honestly saying 30 of them are mine and 30 of them are from my friend XD).
I also bought some ad banners on TWC (this seem to bring about 1-2 thousand views to the comics, but very few subs) and Comicad (gained about 40 000 ad views and only 300 clicks)