I personally recommend a bunch of micro-wbtbs and one long wbtb (15 minutes). As far as the "what if I can't get back to sleep?" then you stayed up too long. I usually wake up, do a little DJ, and then back to sleep quickly except after the 6 hour mark, I usually get up, reread all the entries, do some meditation, and then back to sleep. I would say that this also depends on how tired I am. I don't say "I am going to stay up 5 minutes" or "I am going to stay awake for 15 minutes". I wait until I hit the balance of awake-asleep that is right for LDing!

Mainly posting to see the other responses here.