I say fair play to you, QS, you clearly have considered your options and feel confident in your decision.
I can't say I'm the same; I did want children but ended up not having them. However, I've never felt "broody" in my life - not the way I've seen friends go through it, and not even when I was pregnant. I'd be a fool to discount the advantages of not having kids: more money, MUCH more freedom, better holidays, self-realisation ... selfishness, basically
Equally, I'd be a fool to discount the rewards of parenthood. But it's easier for a selfish adult to find emotional fulfilment by other means, than for a parent to find enough 'me-time'!
In the end, we mostly learn to like what we get. The world's full of accidental parents who wouldn't be without their DC now they've got them. If you don't have children, whether through choice or accident, you come to love the freedom. Out of those who resent their choices, it's the ones with children who do harm.
As long as you're certain of your reasons (eg, you're not covering up a birth phobia or anything) and honestly prefer sterilisation to more temporary solutions, then go for it and good luck :)
By coincidence, several of my friends (mothers) have recently had full hysterectomies and say it's improved their lives no end! I'm not sure why yet but, apart from anything else, a period-free life sounds appealing.