It's not a time bomb as such. It depends on a great many things. How much you use the cube. How hard on it you are. The strength of the cube (remember not all cubes are exactly the same in strength - I bought a storebought Rubik's 3x3 the other day that lasted about 25 seconds before the core shattered, and that's without lube). How much vaselline you used. Where you applied it. And so on.
I suspect you'll get a few months out of it before it shows problems. If you're worried, wait a week, then clean some of it out with a white cloth / white kitchen roll. Any black / discolouration from what you'd expect to see on it is melted plastic.
Please take off topic discussion off this forum. Thanks.