increase checkpoint-interval default from 300 to 1800s, fixes #896
increase checkpoint-interval default from 300 to 1800s, fixes #896

doing a checkpoint can be expensive, if the repo connection is slow and/or
accessed via a network filesystem and/or the repo is large.

thus: don't do it too often.

edgimar/borg,RonnyPfannschmidt/borg,edgimar/borg,raxenak/borg,RonnyPfannschmidt/borg,edgewood/borg,edgimar/borg,RonnyPfannschmidt/borg,edgewood/borg,raxenak/borg,RonnyPfannschmidt/borg,edgewood/borg,raxenak/borg,raxenak/borg,edgimar/borg,RonnyPfannschmidt/borg,edgewood/borg