How long can you keep it - have had some sitting in shed for a few years , one tin is a proprietary brand - the other is Halfords. Wouldn't use it in Furby, but daughter has just joined the VW club with an ancient Driver and if any good -might help her on a tight budget .

I dont think it has an expiry but you're advised to change it every 2 years once its been in your car.

The anti-freeze property doesn't deteriorate, it's the corrosion inhibitors. They are sacrificial and just end up getting used up when they are in a metal engine.

So - left in the can - should be ok - not that I would use it in Furby - but daughter's got an ancient Golf run around - was thinking of her , if she gets a leak - apart from that -it's sat around for a year or two

Depends if it's a metal or plastic can.

Plastic and out of UV it should be fine.

I used to do a proper flush through and then top up as that way any leaks that were going to happen did soon after and you could free all the crap out of the system too.