I have a bottle of P de L which is about mmm maybe six years old. I haven't used it for ages, but had a sudden yearning but it's not really behaving very well in my TWSBI Eco 1.1. (The colour is to die for though.) It's not flowing at all well and I remember it being reasonably wet.
So, it struck me that it may have gone off - any experience with this? I'd be sad to lose the bottle, but would definitely buy some more.