where do you live ?

I've had pla parts outside - in direct sun - for over 6 years.
The parts are good as new - the colour fades slightly, but the actual things stay as flexible and strong as when printed.
That said I live in the uk, so we rarely get summer temps over 30c.

Short of living in soimewhere like the sahara or death valley - not sure where you are going to hit ambient temps of over 60c