So I have to confess to washing straps and being skeptical of washing weakening them. They're tough THICK nylon webbing. Figure you have one of those old school lawn chairs with the THIN nylon webbing, out in the sun and rain, with adults sitting on them - they will last a good while before they start to fray, won't they? And even once they start to fray they will still hold an adults weight.
I can understand in theory how it might weaken them - like vaseline seems innocuous but will eat a hole in a condom - but it just doesn't seem to me like a few cold water washes and line dries, over the life of the seat, is really going to have an effect.
I just don't feel "spot treating" with water really gets them clean. If they're not dirty, they don't need cleaned, but if they are dirty, they really do need cleaned.
It seems to me like having sugars, bacteria, vomit, whatever embedded in the material over time is more likely to cause damage than giving it a thorough wash and dry and being done with it. Especially the vomit part. I guess I can see a strap that has never been washed as being better off than a strap that has been washed... but only of that never been washed strap has also never been dirty.
Is there any proof to washing them being harmful or is it really just "the manufacturer says..."? And if washing them is harmful, has this been compared against straps that have been barfed on and spot cleaned, or never barfed on, never spot cleaned?
The short answer would have been, I toss everything in the washer on cold and line dry it. I don't wash the straps if they don't need it, though.