I dread to think how many bedchairs I have had over the years, Lafuma sunlounger, Fox, Bison, Chub, Badger, (actually a good product!), and Solar.
I think the usual life was around 6 years other than the Lafuma which was only a year until I bit the Fox bullet. (I can go back to the 1990's and before sometimes sleeping on a mat before a bedchair.
The honest answer is that so far the Solar is the best and most comfortable, I haven't had to replace elastic and it hasn't sagged.
Believe me it doesn't happen on every lake, or even on mine all the time. If the ground is really wet we stop cars going round past the inlet (all winter), so a barrow trip might be needed.
Wow, just checking my references on my bedchairs, and found this, a thread on bedchairs:
Strangely enough, I think unless you buy right at the top range, prices aren't too far different or inflated.