I think masturbation for white men is important. It got me hooked to black, interracial cuckold porn for one and that made it much easier to share my girlfriend with black men. Jerking off to that porn only attracts you to the lifestyle more and the release of endorphins makes you addicted. After a few years, you're hooked and you want more (i.e. watching your wife/girlfriend getting blacked in person). So yes, it's important but like anything too much masturbation can be a problem.
If i'm jerking off too much, the pleasure i get from cumming isn't as much. So I have to space out my orgasms and deny myself sometimes so that the next time I get to cum, the pleasure is as intense as the first time i came to interracial cuckold porn. So this brings up chastity and the importance of denial. The angst and jealously of watching your girlfriend/wife's pussy stretch out for another man's bigger cock is part of what makes this lifestlye fun. But you can't jerk off all the time, it'll lessen that pleasure and maybe even turn you off. I've never wanted to eat a creampie from my girlfrend's pussy if i've just came. I need to be denied and horny.
So point is, yes, it's important to deny us white guys the privilege of jerking off whenever we want. But it's important we feel those rush of endorphins while orgasming to associate that cumming pleasure with our girlfriends/wives having sex with other men. It only makes us more willing to submit and stay in the lifestyle. In the cuckold triangle, it's important that everyone wins.