This is interesting, because I have strange issues with reuse with Coopers PET bottles. They seem to 'delaminate' on themselves......
And the plastics engineer in me thinks hard about this. They must be 2 layer, and one layer that helps as the oxygen barrier and also to withstand the pressures. And could be, but might not be, (I need to actually analyse one further as I've not looked at one in a while) injection moulded instead of blow moulded... Sorry I have digressed into geeky land...
Anyways, this delamination seems to make them not so great for re-use because the beers that were in those bottles seem to taste off compared to the same beer in glass bottles.
So for now, until I can save up some more dosh for a corni kegging system, I use swing top bottles and mini-kegs