There shall be a provision that in the case of claim for loss of time for disability, written proof of such loss must be furnished to the insurer within 30 days after the commencement of the period for which the insurer is liable, and that subsequent written proofs of the continuance of such disability must be furnished to the insurer at such intervals as the insurer may reasonably require, and that in the case of claim for any other loss, written proof of such loss must be furnished to the insurer within 90 days after the date of such loss. Failure to furnish such proof within such time shall not invalidate nor reduce any claim, if it shall be shown not to have been reasonably possible to furnish such proof and that such proof was furnished as soon as was reasonably possible. [PL 1969, c. 132, §1 (NEW).]