Mixing dregs of white paint?

[Dinger2]

Being a DIY bodger and a skinflint to boot,I'd appreciate any advice on the subject of mixing the likes of (white) emulsion,vynl silk,vynl matt (inside/water-based) for the purpose of "using-up" old gash paints out of the shed for the painting of concrete gate fence-posts? As long as I can 'refresh', the posts with a fresh 'tosh',I will be happy BUT my question is will this cocktail of paints stay on for at least until next summer? OR because I will use indoor paints will the rain wash it off? and would I be wasting my time?

[modeller]

No problem I do it all the time , but bear in mind the mixture will aquire the characteristic of the least durable depending on the ratios of the mixture.
If the individual paints are usable mixing them has been OK.

[rov1100]

I have often used emulsion paints as an undercoat for oil based paints to be top coated with.

[johnk]

I mix paints all the time. It will probably be OK if it gets time to dry before the next rain, there might be another dry day this summer!!