Vaseline is good to help your eyelashes stay moist and hydrated so in that regard the Vaseline is good for your eyelashes.
However it's a myth that Vaseline helps your eyelashes grow as that is not true.
Adding Vaseline to your eyelashes will not help your eyelashes grow at all but it's still good to use Vaseline on your eyelashes as a moisturizer.
So it will prevent your eyelashes from drying out so you'll have healthier eyelashes when using Vaseline on your eyelashes.
When you moisturize your eyelashes you'll prevent the eyelashes from becoming brittle and possibly breaking.