Plastic carboys

A late comment. I have been using plastic ( polyethelene) 25 litre fermenters ( ie 5 gals imp + headroom) for about 15 years. I use them mainly for secondary fermentation but I also use them for primary fermentation as well.

I nearly always bulk age in 23 litre glbutt carboys ( I have 8 of these and about 40 x 1 gal imp glbutt carboys) but I have, very occasionally, used the "plastic" fermenters for bulk aging some white wines up to about 6 months with no detrimental effects.

These are obviously not "Better bottle" containers but the 10 plastic fermenters I use regularly are various ones I have bought over the years -- specifically designed for home brewing.

The only problem I have had when using them for limited bulk aging is that they have no "narrowing shoulder" being flat topped and so the headspace can be quite considerable -- which means often a topping up of perhaps 4 bottles or so. There is also quite a large surface area of my wine in contact with the limited air in the container . However I do not degas my wines forcefully but let time and patience do that for me, which increases the proctection of my maturing wine.

I must say that handling a full, 23 litre, glbutt container gets more difficult with advancing years but I actually only lift them from the floor level when I am about to bottle.