We bought our first Ryelands in 2007 - three ewe lambs, we bought another two ewe lambs in 2009 to join our one home-bred one, then the same in 2010. In 2011, we had four ewe lambs and have kept three. I sold a ewe in 2012, so have 11 going to the tup this year plus three of this year's ewe lambs that won't.
I've never (touch wood) had one not conceive, although I wouldn't say we have the highest lambing % - about 150%, but I find them good mothers and the lambs are pretty robust.
We still have our three originals - they will go to the tup for the 5th time in November. They all have all their teeth and correct udders and they are almost never lame.
We had a section this year - big single in a smal gimmer. I got the feeding wrong. Both ewe and lamb were fine though - the lamb was 5.5kg at birth
I think what's been said before is right - get the feeding right and you'll be fine, especially in young ewes carrying singles.
I love mine - they are so docile and friendly; they're just a joy to have around. Oh, and the boys are VERY tasty