The message
from "Mike Tickle" contains these words:

Aside from that after two years the boxes need a little more paint
applying - insects have started to eat the inside of them (just a little).
Is there anything (safe) that I can paint them with that might last more
than 2 years, or is 2 years when in contacts with moist compost for 9 months
of the year good (I empty them out over winter).

Line with polythene - solve both problems then.

--
Rusty Hinge
No m'lud, it wasn't a sneg. My joints creak.