I know Doug's father helps out with his reviews, he'll make an appearance, do costume and props, and music.
I know Brad's mom has appeared in a few of his vids, mainly midnight screenings, and Brad tries.
Considering a lot of the reviewers are filmmakers (some more than others) and have video editing skills, they already have abilities and experience that can help them in the long run.
In terms of some of the critics, depending on their focus, they have a never ending supply of things to review. There's always going to be bad video games, comics, cartoons, porn, exploitation films to review. Some of the reviewers made smart choices in picking their focus. With Doug, his main focus is nostalgia (I hate that word) stuff he grew up with and also movies that Ebert gave bad reviews to.
But for Doug that well is drying up. More and more he's focusing on recent films (if his Jurassic World and Pixels reviews are any indication). As well I think there is stuff that he won't touch, stuff that would be nostalgic (he used to do Raiders of the Story Arc where he'd review the first few episodes of a TV series he grew up with--which were honestly funny, even though he liked the shows he would make fun of them) but he hasn't gone back to it. There's only so much of nostalgic things to review and while there are recent bad movies to review those are fresh in our minds.