Timber is a reasonably resilient material, but bad handling & poorly organised storage on job sites could potentially lead to damage & wastage.
It is preferable that you schedule deliveries to minimise storage requirements on site, however if necessary, the following simple rules for on site storage of frames & trusses is recommended:
A leaky roof, guttering or flashing are the most common causes of deterioration in roof trusses, as moisture can infiltrate & cause decay, rot or fungal growth.
Another area of concern for any timber roof truss or wall frame are insects such as termites. The most common method of protection for this scenario is a chemical treatment of the timber.
With regards to roof truss & wall frame maintenance requirements or issues, it is best to have a structural engineer evaluate your individual circumstance. They will use a combination of methods such as visual assessment, moisture meters & fibre optic devices, to evaluate if repair work needs to be carried out.