Re-discovering old oil paints

Rummaging in my capacious paint-box - an old wooden chest which used to house an Ellams screen-print duplicator: so it's quite big - I discovered an aged tube of Rowney's Georgian Monestial Blue, aka Pthalo Blue.  Thought I'd get the top off, a story in itself, and give it a try: it was fabulous!  Beautifully transparent, mixes well with an almost equally old tube of Venetian Red ... and I just don't think my more modern tubes of Pthalo Blue have quite the same quality (could be my imagination, of course) or even colour.   <div> </div><div>Have you discovered old tubes of paint tucked away in the depths of your paintbox, tried them, and been surprised (one way or the other?).  </div><div> </div><div>And why, by the way, do I have around half a dozen tubes of Ivory Black, 30 years old, and more or less untouched (because I don't use black and very rarely did) - did they breed?  </div><div> </div><div>Oh, and finally - did you know, because I didn't, that French Ultramarine and Venetian Red make a fantastic purple?  For some reason, in 40 years of painting I've never mixed the two colours together before ... You learn something new every day in this game; even quite obvious things.  </div><div> </div><div>Oh - and try Mars Violet Deep and Cobalt Blue for a lovely grey.....  You really don't need to buy a huge array of colours, given what you can mix with just a few.  </div>