I have read on some threads that engine oils and obviously Brake fluid break down and/or absorb water after a few years left alone in a bottle and I was just wondering if polishes or waxes do the same? It was just I have a big bottle (3 litres) half used of MER polish which must be over 10-15 years old, so will it be safe to use?

Also does any else use MER polish on here? The other reason I was asking is it's half price in Boyes, £4.99 ish for 1 litre, or it was the last time I looked last week.

Depends on storage conditions and extremes of temperature. I haven't used MER for donkeys ages Used to be fine on solid colours, never tried it on clearcoat.

Some very good waxes on the market now for reasonable money. Collie is good, as are most of the Autoglym and Megs stuff.

I expect its not popular on detailing sites but i still use MER myself from time to time depsite having a massive range of polishes and mine is at least 12 years old , and is still fine, 1 litre will last years!!

Some waxes will sweat solvents so best to keep them cool but i think you are ok with stuff like MER

As said depends on conditions, ive got some AG SRP thats died after sitting in the garage for 2 years as its really runny compared to other bottles of it i have.

some waxes i think can dry out also but that usually more if their left out in the air opened.

It does dry out over the years. I've used MER for years up till the days when metallic paints were mainstream.

Its very good for solid colours but it does cut the paint surface slightly like other cutting polishes so it's not a good idea to use on modern metallics as the the top sealant coat will be eroded if used regulary. Used once or twice of the lifetime of the car you can take out fine scratches buts thats it.

Mer is very handy- as others have said it's a cutting polish, but relatively gentle, so it's good on paint that's been a bit neglected and will get a good shine.

I've had SRP "dissipate" before... the bottom of the bottle was thick and white, and on top was a layer of oily yellow-ish stuff.

Was about 4 years old, stored in a warm shed.

SRP is abrasive as well probably just as much as Mer

Its normal for them to separate a little especially SRP as its full of fillers you can tell i am not a fan i hate the dusty stuff but a good shake should sort it out