AS99
I peridically photocopy mine (monthly or so)...requires A3 copying to get the full spread of the logbook. Since I keep my logbook at home, I keep the copies at work (rolled up in a drawing tube to look like work!) as a " fire copy".
You are wise to consider this, since it one of the very few documents in your possession that is irreplaceable. You might consider creating a fire copy of the few others...your late grandmother's letters, for example, or anything else hand-written and where you don't have access to the originals.