Green Slime only works for about 2 years ish, after that it's has to be replaced. I've never heard of it corroding rims or valves, what I think you'll find is more likely the corrosion due to cheap tyre rim lub/soap and water in the air as many tyre places/stealers don't keep their compressors serviced correctly, when you compress air you get water as a bi product.
What I would recommend is one of the Rema road side repair kits
https://www.ebay.co.uk/itm/Rema-Tip-Top-Tubeless-Tyre-Repair-and-Inflate-On-The-Go-Kit-/302616715140?_trksid=p2385738.m4383.l4275.c10#rpdCntId These are what BMW supply with their bikes.
Getting a puncture is a real pain but is thankfully not a common thing, obviously if you ride where there's a lot of building or up the centre of the road or filter into the hatched areas a lot, you will increase your chances as will letting your tyres get to 1mm. Personally I'm not a fan of Green Slime, yes it can be a real life saver if you're on a touring holiday or constantly in very rural areas. But by definition of how it works you're often not going to know you've got a puncture, it works and works very well for months in some cases but it will start leaking and will fail when you least need it too.
You can use the stuff once you actually get the puncture but you need to be able to inflate the tyre at pace to make it work i.e. compressor or bottles. The other downside is all the mess come tyre changing time, some places now charge you to clean the wheel.
