@(you need an account to see links) Having been getting silenced like once a week for a year straight on multiple accounts, I can tell you that I'm not sure the exact time it takes, but I noticed after about a year of no silences/warnings they reset your record
Um, I've gotten away with this a couple times.
Usually what I'll do is just post my Skype username (usually like "Sky: ________") on a pet lookup, and then I'll just send a neomail to someone and be like "AW HAVE YOU SEEN MY PETS NEW CUSTOMIZATION?" and link them to the lookup.
Sometimes, they're ding dongs and it takes them a couple times to understand what I'm trying to show them, but they get it in the end, and then I just remove the text immediately, I never leave it up for more than a couple minutes.
I've still gotten silenced a couple times, but never since I've started using this method.
Also, in my experience, yes silencings reset, but it takes a while.
But in my case, my main was perma'd and then I got them to lift it, and once they did, it reset my silencings.
So I'm not sure if it's time-related (like if you go a year without a silencing, it resets or whatever) or if it's just because they completely reset my silencings/warnings when they lifted my perma-silence, but yeah.