I also use the battery lock. No lock will absolutely prevent theft but as we know thieves are opportunistic so if my camper is a little better secured than the guy's next door to me I figure I have the better odds.
We live in a subdivision so we have to store our camper at a storage lot. First our batteries were stolen, and then on a separate occasion our propane tanks. Needless to say we store the camper at a different lot now and between the new location and the battery lock, no issues for the past five years.