Running Computer fans at 70°C.

I'm attempting to make a small oven for a friend that needs to maintain 70°C (160°F) and need to circulate air around inside.
Does anyone know or can hazard a guess how well computer fans will be for this? I'm thinking 120mm (5") 12V cheap fans or do I need to go for the high temperature ones?

Thanks,

Mike.

How about a fan from a scrap yard convection oven?

You could use a fan from an old microwave combo oven. As well as the normal plastic fan at the back they have a centrifugal fan with metal blades, to circulate hot air. Or you could make a metal fan to replace the plastic fan on a plastic one that all microwaves have.
I'd imagine a computer fan would warp over time, + there's more to go wrong with it, being brushless. Those old shaded pole motors keep going foreeeeeevvverrrr....
(edit) + with a microwave combo you get some nice high temperature wires for free.