The storage life of petrol is one year when stored under shelter in a sealed container. Once a seal is broken the fuel has a storage life of six months at 20°C or three months at 30°C. The storage life of petrol in equipment fuel tanks is one month. source BP.com
I would like to hear what such additives are, on my cabin I almost every spring use over year petrol ans have had so far no problems.There's plenty of products that can be added to petrol to prolong its storage life and plenty of people seem to get an old chainsaw to run on decades old petrol.
Just google "fuel stabiliser" and loads show up. I think that some 2-stroke oils have a fuel stabiliser in them as well.I would like to hear what such additives are, on my cabin I almost every spring use over year petrol ans have had so far no problems.