go here INSUBSTANTIAL INTERVALS
[87b top] Chizkiyah: As long as there is no empty space on a Get document it is Kosher [even if the spaces are filled in with signatures of relatives who are not valid as witnesses].
Rashi [quoting GM’ Sukhah]: Empty air space is worse than invalid Schach [since open space invalidates the whole structure with 3 Tefachim, while non-Kosher substances only invalidates with 4 Tefachim].
click here D-E-ep Thoughts: It is better to “fill” our time with efforts (even if they do not pan out or yield fruits), rather than leave it “empty” (and waste it on meaningless activities). This idea is especially true in regards to devoting time to spiritual learning and gaining Torah knowledge versus chasing physical pursuits and pleasures (which have no lasting benefits, and most of the time are immediately detrimental as well).