They're a larger breed, so their lifespan isn't going to be like that of a dwarf breed. Breeders have told me anywhere from 5-9 years is typical, but I think they oldest one I've met was 8 when he was put down...
ELops tend not to be the hardiest breed; while I personally have never seen any respiratory issues in my herd, I know of quite a few breeders who have dealt with that, and I've seen my fair share of ELops DQed from the show table for snotty noses. From what I've experienced, abscessing and sore hocks seem to be an issue in the breed, too.
Anyway, point is that being a larger breed, their lifespan is generally shorter than the average rabbit, but like Silver Birch said, it does depend on the individual Lop. If you're concerned about bringing in a healthy bun, the best thing is to be sure and choose to buy from a breeder who culls heavily for health. This is of course important in all breeds, but especially so in the English Lop because of the many health issues they seem to be prone to.