When it is the best time to use them? cuz i've got them for almost 3-4 months in my cargo and they're starting to rust, lol

When you find that really pretty undefended Mega Colossal 22xMR Artifact Oceanic (or a particularly juicy Dyson) and you fail the invade at 90%, then you use a Paradox Generator.

during new years when you can get free race changes

at the same time go after the lone conqueror medal.

yeah...
Ideally: at new year do a massive scan run(save up purgers for it). If you encounter undefended or lightly defended awesome planet(at least VM, at least 20x, prefer C/MC 22x) that, after all buffs/debuffs and maybe some CCM, you can get AT LEAST 40% invasion chance on. If it's below 40%, paradox isn't going to help you much.

Also save up at least one, prefer 3 or so annex decree. In case you find multiple such planets, you can do another one in 4 hours with annex(instead of wasting a paradox for first invasion attempt on a planet)

Thank you all, i think i will wait untill next year lol then leave my legion for a day or two, get 10 Spheres of the New Era, get my Lone Conqueror medal, invading the best planet ill find in my next scan run.

But isnt it a abuse to use all Paradox Generators to get the best artifact in the game?...

paradox is worth more than SNE. The latter only worth a bit of GP while the former is effectively priceless. You should only really consider SNE an awesome addition on top of the invasion clearance, so that it is "best used". But the primary value is more important.

i used mine during the new year i was also had some tough planets lined up was alot of sabbing and cms to

I am doing the same thing going to use all my paradox generators on new years day and get 10 race change devices and go for the lone conquerer medal already gathering the required planets that I want to invade.

Also I may need to save up quite a few tri's and cubes in order to go the 60 levels needed to occupy 15 new planets

Is it an abuse to try to get the best artifact in the first place? If one will help you get the other, I see no problem.

For the record though, I still have one Paradox left after all these years. I have been holding out for a dyson steal to add to my collection of dyson steals.

Thank you all for your comments , one more question: do Paradox Generators reset's Kronyn Erudition ability?

no

Thanks