Is trust REALLY all that important?

So, my fiance has used up his 3 strikes over our ten years together for his dishonesty. He was good for six years (as far as I know, of course). But, he screwed up just over a month ago. Now, he has pretty much has bought himself a permanent title of "liar" as far as I'm concerned. But, he's a sweet and lovely man, and wonderful in so many ways. I love him so much, and I know that he's capable of change. I've seen him do it! So, I may not trust him, but I do have faith in him, and hope in him, and belief that he can stop screwing up. Is that enough?