Exposed braceboard lifespan

[Moondog55]

We are cladding over the top of Foilboard and it may take a while to get around to doing the whole house. Brace ply is cheap and where the weatherboards are rotten and have to be removed during the bathroom reno ( studs need to come out to put the spa in )I will be replacing the weatherboards with a couple of sheets of brace-ply.
Without painting how long does this product last and if w do paint it with a cheap acrylic paint what can I expect as far as weathering ?

[Gaza]

i would put up sarking over it, we use painted ply for hoardings and you get a year or so before the sheets start to swell, even if painted.

[Moondog55]

We would be more than happy with a year, we will have started the foilboard long before then, although if I can find some spare sarking I'll use it

[Bloss]

I simply coat with decking oil and then re-coat if water repelling seems to be diminishing. Have had it last 3 and 4 years . . . edges need to be sealed well though - or filled with external gap filler