I've had non-organic LunaPads for 5 years (but was preggers for 9 months of that time) and while they are kind of stained and ugly by now, they're still fine.
The only part I had to throw away was a liner that got caught in the side-loading washing machine's trap. I'm extremely lazy about looking in or cleaning out that trap, so by the time I found it, it was probably months later and was 1) very smelly and 2) had a hole in it from being wet for months. Ugh. Right in the trash it went.
I use them exclusively (no Diva or anything) and have enough that each gets washed only once or twice - and usually only once - a cycle. Which actually isn't a lot, I work from home and am kind of lazy about changing them. More info than you wanted, I'm sure.